Heritage stations are usually recognized by the listening public as the dominant (or only) AM station broadcasting said format in each market. Heritage stations keep their call letters and/or brands intact for decades. FM stations usually do not qualify, because they often change formats.
In most cases, there is only one heritage station per market. However, there may be more, in the case of multiple stations who have been competing for years. Some examples of major market heritage stations include KDKA Pittsburgh, WOI Des Moines, WBZ Boston, WSB Atlanta, and KMOX St. Louis. However, there are many more AM heritage stations across the US in cities big and small. Often, these smaller daytimer stations are the true heritage stations, as they were once the only local voice in many communities for decades; true pioneers despite having to sign off at sunset. Today, the FCC has given new life to many daytime AM frequencies, by allowing nighttime power at greatly reduced levels. This allows many stations to broadcast 24/7, often with astonishing night coverage. There is a great variety of programming on AM radio for the listener to discover.