Tri-County Area

"Tri-county area" (sometimes "tri-cities" or "tri-state area") is a universal description for a generic American region that's meant to be big, but not too big. A tri-state area is somewhat smaller in landmass and population than regions like The US Eastern Seaboard or the UK Home Counties (which border London). Think Everytown, America on a slightly larger scale.

This trope is Truth in Television for a couple of reasons. In the 18th and 19th Centuries, the people who created American political jurisdictions had a tendency to use rivers as boundaries; those rivers also served as arteries of commerce, so that urban areas grew and expanded across political jurisdictions. On the East Coast of the US, some state boundaries were also drawn so that several states could have access to the Atlantic Ocean.

People who live in these places frequently reside in one jurisdiction and work/attend school/socialize in another, forming a looser proximity community in addition to the existing cities. Later on, media outlets (newspapers, radio and local broadcast television stations) covered these proximity communities as their beats, in part because there were limiting factors, such as wealth, population and a small number of government-issued broadcast licenses. Combining neighbouring cities for social purposes also produces larger talent pools for things like sporting events (say, a tournament between teams from several high schools in the area) and cultural performances (band or choral contests, or forming an amateur theatrical company or symphony orchestra).

Sometimes this trope is used to mock the person using it as part of an Overly Narrow Superlative, including implications of a big fish in a small pond talking up the size of the pond. In reality, most of the "tri-state" references don't refer to the entirety of the three states involved, which underpins this mockery. Also, counties aren't generally very large, so even putting together three counties doesn't add up to a major population center.

The other major use of this trope arises from the practice of organizing emergency services around cities, counties and states. If something big threatens a proximity community (a fleeing felon or a marauding monster or a major storm), the authorities in multiple jurisdictions must be called and their actions coordinated. Invoking this trope can indicate the severity of the threat, much like the proverbial "five-alarm fire". If a blizzard hits, expect local news and weather reporters to say things like, "Downed power lines and limited visibility are affecting the entire tri-state area." In fictional works, characters may be depicted reacting to such local news reports, or they may use the phrase themselves when warning someone else, be it a loved one or a person in authority.

Comics

 * At one point in Ultimate Spider-Man, after the Kingpin sees Spidey's face, one of his people points out that it would be impossible to find him, even if they searched all the teenage boys in the Tri-State Area alone.

Fan Fiction

 * There's a Tri-Cities area in Pretty Cure Heavy Metal, where the Tri-Cities in question are Oriyama, Tsukimiya, and Isuten (in Japan).

Film
"I didn't get you the first time. I was one-time champion of the Tri-state league and the Lesser Antilles. Didn't know one card from the other when I started... but I stayed up at night marking with a pen."
 * You Can't Cheat an Honest Man (1939):

"Good morning, I'm Roger Grimsby. Today, the entire Eastern Seaboard is alive with talk of incidents of paranormal activity. Alleged ghost sightings and related supernatural occurences have been reported across the entire Tri-State area."
 * Ghostbusters:

"Have you been outside lately? Do you know how weird it is out there? We've taken our own head count. There seem to be six million completely miserable assholes living in the tri-state area."
 * Ghostbusters 2:

"Sioux Tower, Rescue One, Roger your Alert Three. We're calling every unit in the tri-state area."
 * Crash Landing: The Rescue of Flight 232:

"Well now, you should buy this one here as well. The Tri-State Defender."
 * Mystery Train:

"On June 17, 1933, five of my finest men were ambushed escorting convicted bank robber Frank Nash to the Federal penitentiary. My men died like dogs in the gutter, and I swore personal vengeance. Mister Hoover told me he wanted these rats that did it exterminated, and that was my only job. Charles Arthur "Pretty Boy" Floyd. George "Machine Gun" Kelly". Lester "Baby Face" Nelson. Wilbur Underhill, "The Tri-state Terror". "Handsome Jack" Klutas. And, of course John Dillinger."
 * Dillinger:

"You've been selected as a preliminary candidate to become our next Nielsen family in the tri-county area."
 * Rain Man

"I'm going to contact the National Poison Control Center to have them alert every ER in the tri-county area..."
 * Snakes on a Plane

"I'm the chief hostage negotiator for the Akron and tri-county area."
 * Best in Show

"We've been the tri-county area's penis retrieval experts for 64 years."
 * The Onion Movie

"Officials are calling for a complete and immediate evacuation of the entire tri-county area."
 * Earthstorm

Literature

 * In Garrison Keillor's Lake Wobegon Days he comments at one point that his composition class supplied the "three county area" with irony.

Live Action TV

 * That '70s Show: In an It's a Wonderful Plot episode, Eric is the assistant manager of the second-largest mattress retailer in the tri-county area.
 * Malcolm in the Middle refers to "the first Polish-American from the tri-county area to play three complete seasons in the majors." The boys enter Lois in the Miss Tri-County pageant.
 * Buffy the Vampire Slayer: An incidental character in the first-season episode "Nightmares" once had the best spider collection in the tri-county area. It's unclear how this was determined...
 * In one episode of The Dukes of Hazzard, Daisy enters the Miss Tri-Counties beauty pageant. This being Hazzard, one segment of the pageant requires the contestants to disassemble and reassemble a carburetor.
 * SCTV's alleged broadcast zone in and around the fictional town of Melonville was frequently referred to as the "Tri-county area".

Professional Wrestling

 * The precursor of Eastern Championship Wrestling/Extreme Championship Wrestling was Philadelphia's Tri-State Wrestling Alliance (presumably the three states were Pennsylvania, New York, and New Jersey). The promotion's high point was probably the August 3, 1991, match between Cactus Jack and Eddie Gilbert; a two-out-of-three-falls affair in which the respective stipulations of the falls were "falls count anywhere", "stretcher," and "steel cage." The bout was third-runner-up for 1991's "Match of the Year" in Pro Wrestling Illustrated magazine (PWI being what it is, the match somehow got enough votes for fourth place despite occurring on an untelevised card in front of a crowd of 562 spectators).

Real Life

 * New York, New Jersey, and Connecticut or New York, New Jersey and Pennsylvania are usually what is meant when used in works set in New York City.
 * Sharpsburg, NC is a town where Wilson, Nash, and Edgecombe counties meet. Part of the town is in each county.
 * Kennewick, Pasco, and Richland are "Tri-Cities" in south central Washington State.
 * There's a Tri-Cities in Tennessee. They consist of Knoxville, Sneedville, and Johnson City, if the history of East Tennessee PBS is to be believed. However, the more popular such grouping consists of Kingsport, Bristol and Johnson City.
 * There's a "Quad Cities" in the USA's Upper Midwest: Davenport and Bettendorf in Iowa, Rock Island and Moline/East Moline in Illinois (The two states are separated by the Mississippi River). Effectively, there are at least five cities involved; East Moline has its own government, and of course the suburbs reach to what were once physically separate communities. The area is rather densely populated, with something like 375,000 people. The local newspaper is The Quad City Times and there's also a symphony orchestra.
 * Sioux City is split by the Missouri and Big Sioux rivers into North Sioux City (South Dakota), South Sioux City (Nebraska), and Sioux City, Iowa.
 * The Other Wiki has this rather impressive list of tri-city areas

Video Games

 * The Tri-Island Area is introduced in The Curse of Monkey Island, and mentioned thereafter. It consists of Mêleé, Booty and Plunder Islands, and their associated archipelagos, and Elaine is the hereditary governor of the lot of them.

Western Animation
"I want tri-state roadblocks! Call forensics and check the scene. I want dogs combing the woods! And some little sprinkly, candy chewies on a cupcake. NOW!"
 * Toy Story takes place in the tri-county area.
 * Parodied in an episode of King of the Hill by Peggy when she exclaims that the kids (Bobby, Connie and Joseph) aren't anywhere in the tri-home area (referring to the Hill, Khan & Gribble residences).
 * Kim Possible lives in a tri-city area, Upperton, Middleton, and Lowerton.
 * Phineas and Ferb has a tri-state area. This is a subversion since the Tri-State area is actually named from it's founder, John P. Tristate.
 * The Tiny Toon Adventures Spring Break movie: