WWJ-AM is regular

Yeah, yeah, yeah. So, KDKA was first (kind of) but they were off air for weeks at a time and only on-air for irregular hours of erratic days. What may perhaps been more important to the long-term business interest in radio was the first regular service:
The Scripps family (James E. Scripps, William J.Scripps began with the test calls 8MK, later WBL-AM, and eventually settled on WWJ-AM, which claims that on Aug. 20, 1920, it became the first radio station in the world to broadcast regularly scheduled programs.

From the second floor of The Detroit News Building one of the brothers spoke the words "This is 8MK calling" then they played two phonograph records, 'Annie Laurie' and 'Roses of Picardy,' a query by an announcer to unseen listeners, 'How do you get it?,' and the playing of taps. The broadcast is thought to have been received in some 30 Detroit homes.

Though the Scripps ran it, the channel was licensed under the Detroit Evening News, another Scripps property. It's been on the air continuously ever since. For the record , the newspaper was established in 1873 by James Scripps, which is also still in operation. The Scripps are a very regular bunch.

James first became interested in radio in 1902 after listening to a Detroit experimental wireless operator, Thomas E. Clark. The Scripps, attended a private demonstration of Clark's system of wireless transmission of Morse code and then helped finance Mr. Clark's work. Meanwhile, William Scripps Jr. (the son of William E. Scripps) a devoted ham radio hobbyist by 1918. It was out of that hobby WWJ-AM grew. http://members.aol.com/jeff1070/70.html