It was hard for a station to determine how many listeners it had in 1925. There were no audience surveys, and so stations could only judge by the volume of mail they received, which could be thousands of letters a day. They knew that about 20% of households had radios, but no one knew the time spent listening or which stations or programs were the most popular. WMAQ operated on 670 kHz almost from its inception. It started at 500 Watts in 1922 on the Fair Department Store building; later moving to the Hotel LaSalle, increaseing to 1 kW in 1925, then to 5 kW in 1928 from a new site in Elmhurst, and finally went to 50 kW from the present Bloomingdale site in 1935. It shared a frequency with WQJ in Chicago until 1928 (eventually buying the other station to gain full time operation). Stations in Boston, Seattle and Waco also used the 670 frequency at times, but by 1929 WMAQ had 670 as a nationwide clear channel. The Federal Radio Commission, which was formed in 1927 to bring order to the airwaves, established 24 clear channel frequencies in 1928. These were divided equitably among all regions of the country. Most of the early clears were major network affiliate stations, and all eventually operated with 50 kW. WMAQ was an NBC affiliate and so it no doubt received preferential treatment by the F.R.C. because of lobbying by NBC.

I'm curious on how many radio listeners WMAQ had back in 1925? Perhaps quite a few at night in what was then '2nd City'? Did they share a frequency with another station(s)? When did the 5KW, 10KW then 50KW stations arrive in Chicago, and the "clear channels" on AM?