What was the fictional locale of your favorite TV sitcom? New York City? Milwaukee? Reno? Cocoa Beach?
Dan Meth, as a part of his series of Popular Culture Charts will help you find them on his U.S.A. Sitcom Map:
There are, of course, a disproportionate number of sitcoms that take place in New York City (although they were probably filmed in Hollywood, California):
I'm guessing that perhaps chart #5 will be a map of Southern California?
UPDATE 4/7: UK TV Series Map at meish.org