As far as TV is concerned, much of the country outside of Los Angeles and New York City is flyover territory.

Those two cities account for just under half of the fictional settings for prime-time television shows going back to 1948, according to a new study by a media agency. California and New York state are settings nearly 60 percent of the time — even though those states make up less than 19 percent of the nation's population.

Alex Keaton of "Family Ties" (search) lived in Columbus, Ohio (search), and Mary Richards of "The Mary Tyler Moore Show" (search) worked at a newsroom in Minneapolis (search), but TV characters are much more likely to join the "Friends" (search) crew for coffee at Central Perk.

"I knew a lot of shows seem to be in New York and L.A., but I didn't expect it to be so concentrated," said Rob Frydlewicz of Carat Insight, a company that studies TV trends for advertisers and conducted the research.

Of the 1,696 cable and network series where the setting was known (some, like NBC's "Scrubs," don't make clear where they're from), a whopping 601 called California home and 412 were set in New York state, the study found.

Wind-swept North Dakota has never had a prime-time show of its own, while Alabama, West Virginia, New Hampshire, Delaware and Vermont had one each.

One theory for the coastal concentration is simple: that's where most TV writers, producers and executives live, so they create what they're familiar with.

The landmarks and large populations of the big cities are also important, said Nina Tassler, CBS entertainment president.

"Both Los Angeles and New York are rich in diversity, culturally and ethnically, so you have great sources to go to for unique stories," she said.

CBS turned to New York for the third installment of its "CSI" series; the first two are in Las Vegas — suddenly a hot TV venue — and Miami. All three of NBC's "Law & Order" dramas are set in New York, and so will the fourth when it premieres in midseason.

A few years ago, NBC was able to run a stunt with its comedies called "blackout Thursday," during which each show — all set in New York — had to deal with the ramifications of a power outage.

TV's historical roots may play a part in the concentration. NBC, and to a certain extent ABC, were long considered urban networks, said Ted Frank, the network's executive vice president for current series. And since the big cities have more potential viewers, why not set a show there?

"There's a danger if the shows are all set in one place," Frank said. "I think there was a time when too many of the (NBC) shows were set in one place and they became interchangeable."

A distant third on the list of most-used settings is Chicago, where the "ER" doctors tend to their wounded.

The locales often become an indelible part of a series' identity: "Dallas" and "WKRP in Cincinnati." "Newhart" in the '80s ran a Vermont inn (its '70s predecessor was set in Chicago). "Designing Women" was based in Atlanta, and the oddballs of "Northern Exposure" lived in Cicely, Alaska. "Laverne & Shirley" capped bottles at a Milwaukee brewery, and "Roseanne" lived in Lanford, Ill.

Civic pride can result: On a pedestrian mall in Minneapolis, there's a statue of Moore's character tossing her hat in the air.

And there's evidence that such local pride also helps ratings, Carat Insight said. The ratings for three current series are more than double in the cities where they are set than in the rest of the country: ABC's "8 Simple Rules" in Detroit, the WB's "Everwood" in Denver and NBC's "The West Wing" in Washington.

When NBC was looking to spin off Frasier Crane's character from the Boston-set "Cheers," producers looked up and down the West Coast and chose Seattle in part because they couldn't recall any other show set there, Frank said.

Otherwise, settings usually aren't the first thing creators think about. Searching for diverse outposts should only be done "as long as it's organic to the show," Tassler said.

There are programs so unique to their big cities that they couldn't be imagined elsewhere: the neurotic characters of "Seinfeld" (search) in New York, for instance, or the show-biz shallowness of "Curb Your Enthusiasm" in Los Angeles.

"As much as many people don't like to be in New York and Los Angeles, they're fascinated by the people who live in these two cities," Frydlewicz said.