ATC number
The American Tower Corporation's identification number for a transmission tower.
The ATC number is a reference to a transmission tower used by American Tower Corporation. It identifies distinct masts and towers used for signal transmission in telecommunications.
American Tower is a private company that owns and leases tower sites rather than a public authority, so the number is a commercial asset key. A tower carries one whether or not it appears in any government register.
The number applies to the tower, not to what stands on it. A single site can carry antennae from several carriers, and they share the one number.
Because the portfolio changes hands, a tower sold to another operator keeps the physical structure but loses its place in this register. A number read from an older source is worth checking against the current site list.