Timeline of Billboard number-one country songs
Billboard magazine has published charts ranking the top-performing country music songs in the United States since 1944. The first country chart was published under the title Most Played Juke Box Folk Records in the issue of the magazine dated January 8, 1944, and tracked the songs most played in the nation's jukeboxes.
Source: Wikipedia — Timeline of Billboard number-one country songs (CC BY-SA 4.0)