Under the Radio Act of 1927 the Federal Radio Commission was formally organized on March 15, 1927. It immediately set about to reorganize the AM broadcast spectrum. Because the situation was so complex, with stations operating on frequencies reserved for Canada, on split channels, and in general wherever the station owner chose to, the first act of the Commission was to continue all radio amateur and ship licenses issued by the Department of Commerce and all coastal, point to point, technical, training, and experimental radio licenses, in order that attention might be concentrated on the pressing problems within the broadcasting band.
On April 24, 1927, the commission granted temporary permits to all broadcasters who held a license, or an extension thereof, issued by the Secretary of Commerce under the act of 1912. That was done mainly to allow stations to operate without rendering their Owners liable to the penalties provided by the radio act of 1927. A preliminary reassignment of frequencies in the New York area was made on April 26, putting stations on a 20 khz separation. This separation had proved inadequate to control interference so it was planned to increase this separation to 50 khz. An order to that effect was issued on May 4, 1927. A major reassignment of radio reassignment of AM broadcast frequencies was announced on May 24, to be effective on June 15, 1927.
This was the first of two major reassignments in two successive years. (The second took place on November 11, 1928.) Smaller modifications included the abovementioned one on April 26, 1927 and another on December 1, 1927.
See this list for a list of involved stations.