Although there are reports that Herrold was making experimental audio transmissions as early as 1909, the best evidence is that it wasn't until July 1912 when he began making regularly scheduled broadcasts. These weekly programs are generally accepted as being the first regular entertainment broadcasts made by radio. More contentious is whether KCBS can be considered the oldest radio station in continuous service, due to the fact that, following the end of World War I, Herrold did not resume regular broadcasting until May 1921. (Other candidates for oldest U.S. radio station include 8MK / WWJ in Detroit, which began regular broadcasts in August 1920; WOC in Davenport, Iowa, which traces its origin to station 9BY, beginning regular broadcasts around September 1920; 9ZAF/KLZ in Denver, with nightly concerts beginning in October 1920; and 8ZZ/KDKA in Pittsburgh, which began operating on November 2, 1920.)