I live near Saratoga Springs, N.Y., aka the Spa City (for the mineral springs) and the Racing City (for the track).
Also in this area: Collar City (Troy), Rug City (Amsterdam), Glove Cities (Gloversville and Johnstown) and Electric City (Schenectady), all named after what used to be their biggest industries. Troy also is proud of being the home of the real Uncle Sam.
I'm in Schuylerville, which used to be Old Saratoga, and every other business in the village is Old (or Olde) Saratoga Somethingorother. (There was a campaign to change the name back to Old Saratoga a few years ago, but it failed.) It's also known as the Turning Point (as in turning point of the American Revolution, because the Battle of Saratoga was fought here).
Then there are the less flattering names: Smallbany, Skankectady, Troylet, Amsterico (that last is because Amsterdam has a large Hispanic population. Hispanics were the last wave of immigrants to move there to work in the carpet mills before they closed).
The town I grew up in, Nashua, N.H., was the Gate City, because it was right on the Massachusetts border.