He began his career by umpiring in the Southern League in 1885, then officiated in the California League from 1886 to 1889, after which he gained his first major league experience in the sole season of the Players' League in 1890. Nearly all games in that era used a single umpire, and the most outstanding officials generally moved from league to league, going wherever the league presidents were perceived as being most supportive, both in salary and in affirming the umpires' field authority. After returning to the California League for the 1891 season, Sheridan umpired in the National League in 1892, then again in the Southern League in 1893.