Salt Lake City was the capital city of Utah. In 2012, it had a population of one million and was the city nearest to Henry van Statten's Vault. As the Ninth Doctor warned, this would make it the first target of a captive Dalek had it escaped the vault. Fortunately, the Dalek was stopped. (TV: Dalek)
Real world location
Though it's possible that a real world location doesn't exist in the same geographic space in the Doctor Who universe, such cases are few and far between. Thus, the map at right is probably a good indicator of the DWU location of Salt Lake City.