There have been three different baseball teams with the St. Louis Browns name. Chronologically, they are:
The St. Louis Brown Stockings were members of baseball's National Association in 1875 and charter members of the National League in 1876-77 before folding.
A third team began as the Milwaukee Brewers in the minor Western League in 1894. In 1900, that league became the American League. In 1901, the team moved to St. Louis and renamed itself the St. Louis Browns. In 1954 the team moved again and is today known as the Baltimore Orioles.