During its early years Union Grounds was the home field for several ballclubs, notably including the Eckford Club, 1862 and 1863 champions of the National Association of Base Ball Players. In 1868, the Mutual Club of New York moved in from Elysian Fields, Hoboken, New Jersey, long-time home of Manhattan clubs but never enclosed. The ballpark's entrance was on Rutledge Street, and a one-story building in right field, 350 feet away from home plate, was in play.

After formation of the first professional league, the National Association of Professional Base Ball Players, Union Grounds was home to the Mutual Club from 1871 to 1876 (the only year as a member of the new National League), Eckford of Brooklyn of the National Association in 1872, and the Atlantic Club of Brooklyn of the National Association from 1873 to 1875. It served as home field for the "Hartford of Brooklyn" team during the 1877 National League season. Some clubs also occasionally staged single games on the grounds, including a season-ending "home" game for the Chicago White Stockings in October 1871, whose own home grounds had been destroyed by the Great Chicago Fire. On July 26, 1878, the final major league game was played on the grounds, with Providence defeating Milwaukee 4-1. The grounds continued to host barnstorming major league clubs, amateur clubs and independent clubs through the 1882 season.

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