Low Power Frequency Modulation
LPFM is a Federal Communications Commission (FCC) established category of radio broadcasting effective as of April 17, 2000. LPFM refers to FM radio stations broadcasting at or below a power of 100 watts within the jurisdiction of the FCC. Stations must be locally owned and non-commercial in nature. The original initiative was spearheaded by the Pirate Radio community in the United States.
The Audio Services Division of the Federal Communications Commission maintains a web site containing information, application forms, and a database for determining if a given location is useable for an LPFM station. In practice, at least the thirty largest metropolitan areas in the United States have no available LPFM frequencies. E.g., Entering the latitude and longitude for Crystal Lake Park, Missouri MO indicates that there are no useable frequencies within 10 km of this town in the St. Louis area.
(Audio Services Division of the FCC web site)
(LPFM Radio Channel Finder)
(USGS Query Form for the United States and its Territories