1936, the era of the Radio

In CBS commissioned a survey to be done of homes with radios based on time zone. This image is the end result.

But ownership of radios was not enough for them to know how often they were being used, and as of result being tuned in to CBS. The next map shows how many of the radios were in use daily.

You can check out more maps and details on this map by checking out J-bary's photoset on flickr.