Alamagordo was a town in New Mexico once visited by the Seventh Doctor, Ace, and Benny. It was likely the county seat, by virtue of the fact that the sheriff's office was there. (PROSE: First Frontier)
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 Alamagordo.