For the U.S., a form of clear channels first appeared in 1922 when the Commerce Department moved stations which had all used three (initially two) frequencies (two for entertainment stations, one for "weather and crop reports") onto 52 frequencies. Two were set aside for low-power local and regional stations, while the large stations in major cities each got their own frequency. A few frequencies were used on both the East and West coasts, which were considered far enough apart to limit interference. At that time, large stations were limited to 1000 watts and some licences were revoked.