At one time in the early days of broadcasting, there were "Shared Time" AM stations in many locations. Over time the AM band expanded so a station that had to share could move full time to a new frequency. If that wasn't available, a wealthier owner would buy off a less-well-off owner, making the richer guy's station full time on that frequency. But there are still a few shared time stations out there. In the Chicago area, two stations still share 1450 and three stations share 1240.
When 1330 in the New York area was still a shared time frequency, one station would sign off in the middle of the day, and the other sign on, different owners, different call letters, different transmitters. I can remember they wouldn't always time it correctly. Sometimes one would go off the air a few minutes before the other signed on. But sometimes the last words of the sign-off recording would still be playing when the other station started its sign-on recording. WEVD was programmed for the Jewish community and also ran other ethnic time-broked shows, while WPOW was a brokered religion station.
So in Washington, 1250 is still sort of shared by two stations, even though they are 275 miles from each other. That distance allows them to both operate at the same time, but not at full non-directional power. Funny that their deal is that Seattle has to operate with reduced power, or directional power, from sunset till midnight. Then Pullman has to sign off at midnight, allowing Seattle to go full power at that point.
I guess the Pullman 1250 can never become an affiliate of Coast to Coast or Red Eye Radio.