Answer: Circus Performers
Today, Billboard Magazine is known as the newspaper which created (and still does) music history. Getting you on the Billboard music charts is the high achievement of many a musician's career. Long before Billboard tracked music, however, it was a newspaper that was much different than the one we know today. In its very first incarnation, which came to the press in 1894, Billboard was a magazine that literally focused on billboards, posters and paper advertisements placed in public places along with poster posters (people who put up promotional posters).
It was originally titled Billboard Advertising and it was a commercial newspaper for advertising. Very quickly, however, the magazine began to carry ads and information about circuses, fairs, carnivals, vaudeville and burlesque shows. From there, the Billboard magazine continued to become the record for the entertainment industry record, and circus artists around the world read it to keep up with what's happening in the industry.
In 1907, they began to cover the film industry, but quickly moved to cover music. In the 1920s, they even created a radio broadcasting station in addition to covering the development of phonograph and radio technology. When the 1930s came out and jukeboxes appeared all over the country, they began publishing what would continue to be the iconic Billboard Music Chart. In the 1960s, the archives theme park / exhibition elements were split into a separate publication, and Billboard completed its conversion to the music industry's icon it is today.