Twin cities are a special case of two cities or urban centres that are founded in close geographic proximity and then grow into each other over time, losing most of their mutual buffer zone.
There are no precise criteria for twin-cityhood, but to be considered twin cities, the cities involved have to have a similar administrative status and somewhat comparable sizes; a
suburb of a much larger population center is usually not considered to form a twin city with it. For example, South San Francisco (population about 65,000) is not considered a twin city with San Francisco (population about 850,000). However, cities considered twinned by proximity do not necessarily match demographically, economically, or politically.
In many historical cases, cities that grew into each other's space lost their individual identities, and the border or barrier originally separating them became almost irrelevant. An 1873 case of twin cities merging to become a united city is
Budapest in Hungary, which began as two settlements ( Buda and Pest) facing each other across the Danube at a strategic fording place along a trade route. In China, the three ancient cities of Hankou, Hanyang, and Wuchang, separated by the junction of the Yangtze and Hanjiang rivers, were joined in 1927 into the single entity of Wuhan.
Twin cities may share an airport into whose
airport codes are integrated the component initials, e.g., DFW ( Dallas–Fort Worth), LBA ( Leeds– Bradford), MSP ( Minneapolis– Saint Paul, Minnesota), RDU ( Raleigh and Durham, NC), and CAK ( Akron– Canton, Ohio).
In some cases, such as
Albury/ Wodonga in Australia, the two cities are permanently divided by a state border, often one that strictly adheres to a geographical landmark, such as the Murray River that divides New South Wales from Victoria, and thus Albury from Wodonga. In other cases twin cities can be divided by an international border, but retain a cultural and historical similarity, for example Haparanda ( Sweden) and Tornio ( Finland), Leticia ( Colombia) and Tabatinga ( Brazil) or Valga ( Estonia) and Valka ( Latvia).
Cross-border example of twin cities:
Plaza Internacional of the Frontera de la Paz. On the left, Santana do Livramento (Brazil); on the right, Rivera (Uruguay).
Augusta, Georgia and North Augusta, South Carolina
Alcoa and Maryville, Tennessee
Allentown and Bethlehem, Pennsylvania [n 5]
Auburn and Lewiston, Maine
Auburn and Opelika, Alabama
Benton Harbor and St. Joseph, Michigan
Bloomington and Normal, Illinois [n 6]
Bluefield, Virginia and Bluefield, West Virginia [n 7]
Boise and Nampa, Idaho
Bossier City and Shreveport, Louisiana [n 8]
Bridgeport and New Haven, Connecticut
Bristol, Tennessee and Bristol, Virginia
Bryan and College Station, Texas [n 9]
Centralia and Chehalis, Washington
Charleston and North Charleston, South Carolina
Champaign and Urbana, Illinois [n 10]
College Corner, Ohio and West College Corner, Indiana
Colorado City, Arizona and Hildale, Utah
Conover and Newton, North Carolina
Crystal City and Festus, Missouri
Dallas and Fort Worth [n 11]
Dover and New Philadelphia, Ohio
Duluth, Minnesota, and Superior, Wisconsin [n 12]
Durham and Raleigh, North Carolina [n 13]
Easton, Pennsylvania and Phillipsburg, New Jersey
Fargo, North Dakota, and Moorhead, Minnesota [n 14]
Fitchburg and Leominster, Massachusetts
Fort Myers and Cape Coral, Florida
Grand Forks, North Dakota and East Grand Forks, Minnesota
Greenville and Spartanburg, South Carolina [n 15]
Gulfport and Biloxi, Mississippi [n 16]
Hartford and Waterbury, Connecticut
Houghton and Hancock, Michigan
Killeen and Temple, Texas
Lafayette and West Lafayette, Indiana
Lancaster and Palmdale, California [n 17]
Lansing (west), and East Lansing, Michigan
Lewiston, Idaho and Clarkston, Washington
Macon and Warner Robins, Georgia
Marinette, Wisconsin and Menominee, Michigan
Midland and Odessa, Texas [n 18]
Minneapolis and Saint Paul, Minnesota [n 19]
Monroe and West Monroe, Louisiana
Montague and Whitehall, Michigan
Negaunee and Ishpeming, Michigan
Norfolk and Virginia Beach, Virginia
Palmer and Wasilla, Alaska
Portland and South Portland, Maine [n 20]
Portland, Oregon and Vancouver, Washington
Petersburg and Richmond, Virginia [n 21]
Phoenix and Mesa, Arizona
Reno and Sparks, Nevada
Roanoke and Salem, Virginia Roanoke Valley
San Francisco and Oakland, California
Scranton and Wilkes-Barre, Pennsylvania [n 22]
Seattle and Tacoma, Washington
Sherman and Denison, Texas [n 23]
South Bend and Mishawaka, Indiana
Stamford, Connecticut and Norwalk, Connecticut
St. Petersburg and Tampa, Florida [n 24]
Texarkana, Arkansas and Texarkana, Texas [n 25]
Union City, Indiana and Union City, Ohio
Wahpeton, North Dakota and Breckenridge, Minnesota Yuba City and Marysville, California
Mexico—United States border
San Diego, California, United States and Tijuana, Baja California, Mexico
Calexico, California, United States and Mexicali, Baja California, Mexico
Yuma, Arizona, United States and San Luis Río Colorado, Sonora, Mexico
Nogales, Arizona, United States and Nogales, Sonora, Mexico
Douglas, Arizona, United States and Agua Prieta, Sonora, Mexico
Columbus, New Mexico, United States and Las Palomas, Chihuahua, Mexico
El Paso, Texas, United States and Ciudad Juárez, Chihuahua, Mexico
Presidio, Texas, United States and Ojinaga, Chihuahua, Mexico
Del Rio, Texas, United States and Ciudad Acuña, Coahuila, Mexico
Eagle Pass, Texas, United States and Piedras Negras, Coahuila, Mexico
Laredo, Texas, United States and Nuevo Laredo, Nuevo León, Mexico
McAllen, Texas, United States and Reynosa, Tamaulipas, Mexico Brownsville, Texas, United States and Matamoros, Tamaulipas, Mexico
Canada–United States border
Point Roberts, Washington and Tsawwassen, British Columbia
Pembina, North Dakota and Emerson, Manitoba
International Falls, Minnesota and Fort Frances, Ontario
Sault Ste. Marie, Michigan and Sault Ste. Marie, Ontario
Port Huron, Michigan and Sarnia, Ontario
Detroit, Michigan and Windsor, Ontario
Niagara Falls, New York and Niagara Falls, Ontario
Buffalo, New York and Fort Erie, Ontario
Derby Line, Vermont and Stanstead, Quebec Calais, Maine and St. Stephen, New Brunswick
Examples, sharing names or similar names, across an international border include:
Chuí, Brazil; Chuy, Uruguay
Niagara Falls, Ontario, Canada; Niagara Falls, New York, United States
North Portal, Saskatchewan, Canada; Portal, North Dakota, United States
Sault Ste. Marie, Ontario, Canada; Sault Ste. Marie, Michigan, United States
Boquillas del Carmen, Coahuila, Mexico; Boquillas, Texas, United States
Naco, Sonora, Mexico; Naco, Arizona, United States
Nogales, Sonora, Mexico; Nogales, Arizona, United States
Nuevo Laredo, Tamaulipas, Mexico; Laredo, Texas, United States
Nuevo Progreso, Río Bravo, Tamaulipas, Mexico; Progreso, Texas, United States
San Luis Río Colorado, Sonora, Mexico; San Luis, Arizona, United States
Tecate, Baja California, Mexico; Tecate, California, United States Calexico, California; Mexicali, Baja California — see Calexico–Mexicali
Pairs with unrelated names
San Diego and Tijuana — see San Diego–Tijuana
Detroit, Michigan and Windsor, Ontario — see Detroit–Windsor
Douglas, Arizona and Agua Prieta, Sonora
Brownsville, Texas and Matamoros, Tamaulipas — see Matamoros–Brownsville Metropolitan Area
Eagle Pass, Texas and Piedras Negras, Coahuila
Del Rio, Texas and Ciudad Acuña, Coahuila
Presidio, Texas and Manuel Ojinaga, Chihuahua El Paso, Texas and Ciudad Juárez, Chihuahua — see El Paso–Juárez
Surat and Navsari, India
Guwahati and Dispur, India
Bangalore and Hosur, India
Ahmedabad and Gandhinagar, India 
Allahabad and Naini, India 
Varanasi and Mughalsarai, India
Cuttack and Bhubaneswar, India 
Munger and Jamalpur, India 
Durg and Bhilai, India 
Hubli and Dharwad, India 
Vijayawada and Guntur, Andhra Pradesh, India 
Kankroli and Rajsamand, India 
Kochi and Ernakulam, India  
Thrissur and Guruvayur, India 
Kolkata and Howrah, India 
Mumbai and Navi Mumbai, India 
Noida and Greater Noida, India 
Pune and Pimpri-Chinchwad, India 
Sangli and Miraj, India
Harihar and Davangere, Karnataka, India
Jalpaiguri and Siliguri, West Bengal, India
Asansol and Durgapur, West Bengal, India
Shivamoga and Bhadravati, Karnataka, India
Hyderabad and Secunderabad, Telangana state, India
Ranchi and Hatia, India 
Tiruchirappalli and Srirangam, Tamil Nadu, India
Bhavani and Komarapalayam, Tamil Nadu, India
Tirunelveli and Palayamkottai, Tamil Nadu, India 
Pondicherry and Cuddalore,India
Seleucia and Ctesiphon, Iraq [n 27]
Tel Aviv and Jaffa, Israel
Okayama and Kurashiki, Japan [n 28]
Tsukuba and Tsuchiura, Japan [n 29]
Nasushiobara and Otawara, Japan [n 30]
Kamisu and Kashima, Japan [n 31]
Beirut and Jounieh, Lebanon
Kathmandu and Lalitpur, Nepal
Nepalgunj and Kohalpur, Nepal
Tulsipur and Ghorahi, Nepal
Dharan and Itahari, Nepal
Butwal and Tilottama, Nepal
Dhaka and Narayanganj, Bangladesh
Guangzhou and Foshan, People's Republic of China
Macau and Zhuhai, People's Republic of China
Rawalpindi and Islamabad, Pakistan
Peshawar and Mardan, Pakistan
Jhelum and Sarai Alamgir, Pakistan
Ramallah and al-Bireh, Palestine
Dipolog and Dapitan, Philippines
Taipei and New Taipei, Taiwan
Dammam and Khobar, Saudi Arabia
Seoul and Incheon, South Korea
Bangkok and Nonthaburi, Thailand
Chiang Mai and Lamphun, Thailand Songkhla and Hatyai, Thailand
Nørresundby and Aalborg, Denmark
Bournemouth and Poole, United Kingdom
Bratislava and Vienna, Austria, Slovakia
Brighton and Hove, United Kingdom
Chatham and Rochester, United Kingdom 
Leeds and Bradford, United Kingdom
Manchester and Salford, United Kingdom
Newcastle-upon-Tyne and Gateshead, United Kingdom
Porto and Vila Nova de Gaia, Portugal
Póvoa de Varzim and Vila do Conde, Portugal
Ludwigshafen and Mannheim, Germany
Mainz and Wiesbaden, Germany
Ulm and Neu-Ulm, Germany
Sindelfingen and Böblingen, Germany
Frankfurt and Offenbach, Germany
Nuremberg and Fuerth, Germany
Rotterdam and The Hague, The Netherlands
Fredrikstad and Sarpsborg, Norway
Porsgrunn and Skien, Norway
Sandnes and Stavanger, Norway
Słupsk and Ustka, Poland
Novi Sad and Petrovaradin, Serbia
Zemun and New Belgrade, Serbia
Plovdiv and Asenovgrad, Bulgaria
Alcobendas and San Sebastián de los Reyes, Spain
Coslada and San Fernando de Henares, Spain
Santa Cruz de Tenerife and San Cristóbal de la Laguna, Spain
Elda and Petrer, Spain
Gothenburg and Mölndal, Sweden
Jönköping and Huskvarna, Sweden
Athens and Piraeus, Greece Frejus and Saint-Raphaël, France
Bad Radkersburg, Austria and Gornja Radgona, Slovenia
Comines, Belgium and Comines, France
Mouscron, Belgium and Tourcoing, France
Wervik, Belgium and Wervicq-Sud, France
Těšín, Czech Republic and Cieszyn, Poland
Copenhagen, Denmark and Malmö, Sweden
Narva, Estonia and Ivangorod, Russia
Valga, Estonia and Valka, Latvia
Tornio, Finland and Haparanda, Sweden
Hendaye, France and Irun, Spain
Strasbourg, France and Kehl, Germany
Frankfurt (Oder), Germany and Słubice, Poland
Görlitz, Germany and Zgorzelec, Poland
Guben, Germany and Gubin, Poland
Heringsdorf, Germany and Świnoujście, Poland
Esztergom, Hungary and Štúrovo, Slovakia
Gorizia, Italy and Nova Gorica, Slovenia
Kerkrade, The Netherlands and Herzogenrath, Germany
Komárno, Slovakia and Komárom, Hungary Slavonski Brod, Croatia and Bosanski Brod, Bosnia and Herzegovina
Albury and Wodonga, Australia
Bentleigh and Carnegie, Australia
Canberra and Queanbeyan, Australia
Gold Coast and Tweed Heads, Australia
Forster and Tuncurry, Australia
Harden and Murrumburrah, Australia
Kalgoorlie and Boulder, Australia
Napier and Hastings, New Zealand
Perth and Fremantle, Australia
Townsville and Thuringowa, Australia Parramatta and Sydney, Australia
Guadalajara; Tlaquepaque; Zapopan, Jalisco, Mexico
Brisbane; Logan; Ipswich, Queensland Australia
Chandigarh; Mohali; and Panchkula, India 
Vijayawada; Amaravati; and Guntur, India
Iron River, Caspian, and Gaastra, Michigan
Bhaktapur; Kathmandu; and Patan, Nepal
Stockholm; Solna; and Sundbyberg, Sweden
San Jose; San Francisco; and Oakland, California [n 32]
New York, New York; Newark; and Jersey City, New Jersey
Gdańsk; Gdynia; and Sopot, Poland — see Tricity, Poland
Greensboro; Winston-Salem; and High Point, North Carolina, the cities' collective metropolitan area is often called the Piedmont Triad
Raleigh; Durham; and Chapel Hill, North Carolina, the cities' collective metropolitan area is often called the Research Triangle
Dallas; Fort Worth; and Arlington, Texas
Warangal; Hanamkonda; Kazipet, India
Pasco; Richland; and Kennewick, Washington
Dubai; Sharjah; and Ajman, United Arab Emirates
Khartoum; North Khartoum; and Omdurman, Sudan
Kitchener; Waterloo; and Cambridge, Ontario, the cities' collective metropolitan area is often called the Kitchener-Waterloo or simply K-W
Bay City; Saginaw; and Midland, Michigan, the cities' collective metropolitan area is often called Saginaw Valley and the MBS Regions
Temiskaming Shores, Ontario, Canada - Amalgamated the former municipalities of Cobalt, Haileybury and New Liskeard
Wejherowo; Rumia; and Reda, Poland — see Kashubian Tricity
Ironwood; Bessemer; and Wakefield, Michigan Binghamton; Endicott; and Johnson City, New York, the cities' collective metropolitan area is often called the Triple Cities
Allentown/ Bethlehem, Pennsylvania and Easton, Pennsylvania/ Phillipsburg, New Jersey; the collective area is often called the Lehigh Valley
Quad Cities of Davenport and Bettendorf, Iowa, and Rock Island and Moline, Illinois. It also includes a fifth member, East Moline, Illinois. The
Florence-Muscle Shoals Metropolitan Area in Alabama is locally referred to as "the Quad Cities", with Florence, Muscle Shoals, Sheffield, and Tuscumbia. Formerly, when Muscle Shoals was a mere village, this region was known a "Tri-Cities", Alabama. In fact, all except Florence are incorporated as towns. The
Quad Cities of Minnesota consist of Virginia, Eveleth, Gilbert, and Mountain Iron. The cities of
Pullman, Washington, Moscow, Idaho, Clarkston, Washington, and Lewiston, Idaho have marketed themselves as "Quad Cities."  Pattaya-Chonburi Metropolitan Area consists of the City of Pattaya, Town of Chonburi, Portal town of Laem Chabang and Town of Sattahip on the west coast of Chonburi Province, Thailand
More than four cities
In the US state of
Virginia: Norfolk, Chesapeake, Hampton, Newport News, Portsmouth, Suffolk, and Virginia Beach; the cities' collective metropolitan area is often called Hampton Roads
Ruhr district ( Germany): consisting of Dortmund, Essen, Duisburg, Bochum, Oberhausen, Mülheim, Bottrop, Gelsenkirchen and Herne in its core. In the US states of
Illinois and Iowa: Davenport and Bettendorf in Iowa; Rock Island, Moline and East Moline in Illinois. In
Malaysia: the cities of Kuala Lumpur, Petaling Jaya, Subang Jaya, Puchong, Shah Alam, Klang, Port Klang, Putrajaya, Cyberjaya, and Kajang have formed a huge metropolitan area (around the size of Singapore) known as Greater Kuala Lumpur. In
India: the cities of New Delhi, Noida, Greater Noida, Ghaziabad, Gurgaon and Faridabad have formed a huge metropolitan area known as National Capital Region (India). In the US states of
Michigan and Wisconsin sit the 6 cities of Iron Mountain, Kingsford, Quinnesec, Norway (in Michigan), Aurora, and Niagara (in Wisconsin). The area is collectively known as the Iron Mountain Area. The Michiana area, in the states of Indiana and Michigan, consisting of the cities of South Bend, Mishawaka, Elkhart, Granger, Michigan City, Goshen, La Porte ( Indiana), New Buffalo, Buchanan, Niles, Berrien Springs, St. Joseph, Benton Harbor, and Dowagiac ( Michigan)
Examples of cities formed by amalgamation
Delhi, India: What used to be Old Delhi, New Delhi, and a collection of smaller villages has now grown into the current megalopolis that we see today, also known as the National Capital Region (NCR) In
Telangana, India, the cities of Hyderabad and Secunderabad are merged to form Greater Hyderabad.
Lahore, the second largest city of Pakistan, has, as of 2013, grown out so much that small towns by this giant city, such as Shahdara, have been absorbed in its city limits.
Wuhan in China consists of the towns of Wuchang, Hankou, and Hanyang in Hubei Province.
Islamabad, the capital city of Pakistan, has been expanded to include smaller towns including Rawat in its territory.
Bangkok, the capital and largest city of Thailand, was created in 1971, when the previous Bangkok province (Phra Nakhon) was merged with Thonburi province. The former cities of
Taoyuan and Zhongli, Taiwan, which merged along with the entire county in 2014 to form a single municipality city of Taoyuan, the two cities sit directly next to each other and shares almost the same population.
Fukuoka in Japan, a city of 1.4 million people, formerly the twin cities of Hakata and Fukuoka until the late 19th century.
Saitama in Japan, a city of 1.2 million people, created in 2001 by the merger of the cities of Urawa, Omiya, Yono, and later Iwatsuki. Urawa and Omiya could formerly have been considered twin cities.
Kitakyushu in Japan, a city of 900,000 people, created in 1963 by the merger of Yahata, Kokura, Moji, Wakamatsu, and Tobata. Yahata and Kokura had formerly been major cities in their own right. The cities of Saigon and Cholon merged in 1931 to form a single city named Saigon-Cholon; in 1956, the name Cholon was dropped and the city became known as Saigon (now Ho Chi Minh City).
London grew from its cores in the City of London and the City of Westminster to encompass many other towns and villages within neighbouring counties and absorbed almost the whole of Middlesex county.
Budapest is the amalgamation of Buda, Pest and Óbuda.
Berlin (Berlin and Cölln), in Germany
Duisburg (Duisburg and Hamborn, 1929–1935 called Duisburg-Hamborn), in North Rhine-Westphalia, Germany
Wuppertal ( Barmen and Elberfeld), in North Rhine-Westphalia, Germany
Manchester and the city of Salford, England in the Metropolitan County of Greater Manchester (formerly in Lancashire).
Stoke-on-Trent was created in 1910 from the towns of Burslem, Hanley, Tunstall, Longton, Fenton and Stoke, taking its name from the latter. Neighbouring Newcastle-under-Lyme remains a separate town.
Eindhoven merged with five neighbouring municipalities ( Woensel, Tongelre, Stratum, Gestel en Blaarthem and Strijp) into the new Groot-Eindhoven ("Greater Eindhoven") in 1920. The prefix "Groot-" was later dropped. Madrid evolved by absorption of other towns (like Tetuán de las Victorias, Vallecas, Chamartín de la Rosa or Aravaca) 
Richmond (Richmond and Manchester) in central Virginia
Cleveland (Cleveland and Ohio City) in Ohio
Minneapolis. St. Anthony (not to be confused with St. Anthony Village, a modern city which is a suburb) was a twin city to Minneapolis in the two cities' youth. Minneapolis annexed St. Anthony in the late 1800s.
New York City (five boroughs, historically especially between Manhattan and Brooklyn)
Jersey City, New Jersey, was incorporated in 1820, and slowly grew by annexing surrounding municipalities: Van Vorst Twp. (1851), Bergen City (1869), Hudson City (1869), Bergen Twp. (1869) and finally Greenville Twp. (1873).
Fremont, California was formed in 1956 by the combination of the five towns of Centerville, Irvington, Niles, Mission San Jose, and Warm Springs, California. The town of Newark has always refused to merge into Fremont, and Newark is completely surrounded by Fremont. What is now the city of
Winston-Salem, North Carolina was once two separate towns called Winston and Salem that were combined into one.
Ottawa, Ontario, was given its large area by the amalgamation in 2001 of the old City of Ottawa, the suburbs of Nepean, Kanata, Gloucester, Rockcliffe Park, Vanier and Cumberland, Orleans, and the rural townships of West Carleton, Osgoode, Rideau, and Goulbourn
Gatineau, Quebec, formed by the amalgamation of the old City of Gatineau, City of Hull, City of Aylmer, City of Buckingham and the Municipality of Masson-Angers all facing the City of Ottawa, Ontario from the north shore of the Ottawa River.
Toronto formed by an amalgamation of the Old Toronto with East York, Etobicoke, North York, Scarborough and York, which were themselves products of earlier amalgamations.
Thunder Bay, Ontario ( Fort William and Port Arthur).
Lloydminster, Canada, on the Saskatchewan- Alberta border, was formed as a single entity in 1903, when both future provinces were part of the Northwest Territories, but was divided into two separate entities in 1905 because the border between the newly created provinces bisected the community. In 1930, the two towns were reunited as a single town under the shared jurisdiction of both provinces, and Lloydminster was reincorporated as a single city in 1958.
Halifax and Dartmouth (Canada) were forcibly merged in 1996 along with Bedford and Halifax County to create the Halifax Regional Municipality.
Saguenay, Quebec ( Chicoutimi, Jonquière, et al.)
Bellingham, Washington was formed from four cities, Fairhaven, Sehome, Bellingham and Whatcom.
Lincoln City, Oregon was formed in 1965 by merging the extant seaside towns of Oceanlake, Delake, and Taft, with the adjoining unincorporated areas of Nelscott and Cutler City.
Pittsburgh annexed Allegheny City, which is now the quarter of the city that lies north of the Allegheny and Ohio rivers. Also annexed was Birmingham, now referred to as the "South Side".
Bethlehem, Pennsylvania, which absorbed the cities of South Bethlehem, and West Bethlehem. The former Bethlehem and South Bethlehem are situated in Northampton County, and West Bethlehem is in Lehigh County. As a result, present-day Bethlehem straddles the county line.
Montreal, Quebec, was merged with the other 27 communities on the Island of Montreal by an act in the Quebec Parliament in 2002. Following a change in the provincial government, several communities later voted via referendum to de-merge and there are now a total of 15, leaving Montreal merged with the other 12.
Kingston, Ontario was amalgamated in 1998 with the neighboring Kingston and Pittsburgh Townships.
Winnipeg, Manitoba amalgamated with 12 surrounding municipalities and its metropolitan corporation in 1971 under what was referred to as unicity reforms in local government restructuring.
Park Hills, Missouri was formed in 1994 by a four-way municipal merger involving the cities of Flat River, Elvins, and Esther, plus the village of Rivermines.
Helena-West Helena, Arkansas was formed in 2006 by the merger of the previous cities of Helena and West Helena.
Greater Sudbury, Ontario, was formed in 2001 by the amalgamation of the former Regional Municipality of Sudbury, comprising the municipalities of Sudbury, Nickel Centre, Valley East, Capreol, Rayside-Balfour, Onaping Falls and Walden, plus a number of previously unamalgamated townships. The amalgamation made it the most populous city in the Northern Ontario region.
Boston, Massachusetts is made up of the former towns of Boston, Dorchester, Brighton, Roxbury, Charlestown, and Hyde Park.
Port Alberni, British Columbia was formed in 1967 when Alberni and Port Alberni, merged to become one city. Iron River, Michigan absorbed the nearby city of Stambaugh and village of Mineral Hills in July 2000.
Fictional twin cities
Gotham City (the home of Batman) and Metropolis (the home of Superman) have sometimes been presented as twin cities, mainly in 1970s and 1980s stories by DC Comics. In stories presenting them as twin cities, Gotham City and Metropolis are located on opposite sides of a large bay (identified as Delaware Bay in 1990's ), with both cities linked by the Metro-Narrows Bridge, The Atlas of the DC Universe a  suspension bridge resembling New York City's Verrazano-Narrows Bridge.  
Central City and Keystone City, from the current , are shown as twin cities. Before the 1985-86 miniseries Flash comics , Central and Keystone are presented as located in the same space but on different Crisis on Infinite Earths parallel Earths. 
Ankh-Morpork, from Terry Pratchett's novels, is referred to as "the twin cities of proud Ankh and pestilent Morpork" Discworld 
Duckburg and St. Canard were depicted in the cartoon as sister cities connected by a bridge, very similar to Darkwing Duck Oakland and San Francisco.   Helium, from the
series of novels by Barsoom Edgar Rice Burroughs, consists of the twin cities Greater Helium and Lesser Helium.  Besźel and Ul Qoma in China Miéville's novel are intertwined twin city-states in Eastern Europe whose inhabitants have trained themselves to only see the city they live in and unsee the city they don't. The City & the City
^ Separated by the
Nile, each city is the respective capital of its governorate ( Cairo and Giza). The two communities are the main cities of Greater Cairo. They are respectively the most populous city and third most populous city in Egypt.
^ Separated by the
North Saskatchewan River. While the communities are commonly referred to by the collective "The Battlefords," they retain distinctive identities.
^ Main cities of
Metropolitan Halifax, they are geographically separated by Halifax Harbour
^ form the
National Capital Region, geopolitically separated by the Ottawa River
^ Two of the three anchor cities of the
Lehigh Valley in eastern Pennsylvania, an area that spills over into neighboring New Jersey.
Bluefield micropolitan area.
Shreveport–Bossier City metropolitan area.
College Station–Bryan metropolitan area.
Champaign was originally known as West Urbana but has since outgrown its neighbor. See Champaign–Urbana metropolitan area.
^ Twin cores of the
Metroplex of northern Texas.
^ Nicknamed the
Twin Ports, these form the world's largest freshwater port.
^ Two anchor cities of the three-city
Research Triangle area.
^ The two largest cities of
Upstate South Carolina. Their shared international airport is named after both cities ( Greenville–Spartanburg International Airport).
Gulfport–Biloxi metropolitan area.
^ The principal cities of the
Antelope Valley and High Desert in California.
^ Nicknamed the
Petroplex in a nod to the DFW region's nickname, as well as its strong reliance on the oil industry.
^ Also known as the
^ Share the
Portland International Jetport (buildings/terminal in one city, runways in the other) and the Port of Portland and retain separate identities.
^ One perhaps more suburban; see
Greater Richmond Region.
^ The core cities of the
Wyoming Valley in northeastern Pennsylvania.
Sherman–Denison metropolitan area.
^ Main cities of the
Tampa Bay Area.
^ The cities meet at the border between
Texas and Arkansas, and their name is a portmanteau of those states' names as well as that of Louisiana, whose border lies approximately 25 miles to the south. See Texarkana metropolitan area and Ark-La-Tex.
^ Until 1930, the community, divided by the
Alberta- Saskatchewan border, was two separate, adjacent towns. However, with the Town of Lloydminster Acts in administration the large town became integrated while still bi-provincial.
^ Formed historic
^ Kurashiki is somewhat more of a suburb
^ Co-centers of a shared major metropolitan area.
^ Co-centers of a shared micropolitan area.
^ Co-centers of a shared micropolitan area.
^ the principal cities of the
San Francisco Bay area.
"10 Twin Towns and Sister Cities of Indian States". walkthroughindia.com . Retrieved . 9 January 2014
^ a b c d e f g h i j k l m n o
"10 Twin Towns and Sister Cities of Indian States". walkthroughindia.com . Retrieved . 9 January 2014
Weather story from 2006 The Hindu Business Line. Retrieved 2006-12-31
      
^ "It's a wise man who knows where Chatham ends and Rochester begins."
"Tricity residents to get Emaar MGF's Central Plaza soon". . Jan 6, 2014. The Financial Express
"Quad Cities too generic a name for ID, WA cities". . 28 April 2010 The Seattle Times . Retrieved . 22 January 2013
#451, Action Comics DC Comics, September 1975
New Adventures of #22, Superboy DC Comics, October 1981
#259, World's Finest Comics DC Comics, October–November 1979
The Flash (volume 1) #123, DC Comics, September 1961
^ See e.g. the introduction of The Hogfather
q:Terry Pratchett's Hogfather
Starr, Joe (2015-08-05). "Nerd Rabbit Hole: A Guide To Disney's Duck Universe". Pajiba . Retrieved . 2018-05-10
"San Francisco–Oakland Bay Bridge". www.visitcalifornia.com . Retrieved . 2018-05-10
^ Burroughs, Edgar Rice (1917).
. A Princess of Mars A. C. McClurg & Co. pp. 279–80, 305, 313–14.