You can request a call sign along with getting your license from the FCC. The process has changed over time, but many (most?) call signs have some sort of historical connection to something: e.g. KRON was broadcast from the SF Chronicle newspaper building, WRCT is Carnegie Mellon's University's station (originally Radio Carnegie Tech, from before it was CMU). https://en.wikipedia.org/wiki/Call_signs_in_the_United_State...