In the 1930s, radio in the United States was dominated by three companies: the Columbia Broadcasting System (CBS), the Mutual Broadcasting System and the National Broadcasting Company (NBC). The last was owned by electronics manufacturer Radio Corporation of America (RCA), which owned two radio networks that each ran different varieties of programming, NBC Blue and NBC Red. The NBC Blue Network was created in 1927 for the primary purpose of testing new programs on markets of lesser importance than those served by NBC Red, which served the major cities, and to test drama series.