John P. Cassidy
- Bats Right, Throws Left
- Height 5' 8", Weight 168 lb.
- Debut April 24, 1875
- Final Game August 12, 1885
- Born 1857 in Brooklyn, NY USA
- Died July 2, 1891 in Brooklyn, NY USA
John Cassidy had one great season in an otherwise ordinary career. In 1877, at age 20, he hit .378 for the 1877 Hartford Dark Blues, their last season as a major league team. Cassidy's batting average was second in the league, his slugging percentage was third in the league, and his Adjusted OPS+ was second in the league behind Deacon White.
Mostly an outfielder, Cassidy also pitched 32 games, going 1-20 in 1875.
In 1886 he became a politician, getting elected to the Brooklyn Democratic General Committee. In 1887 it was said he was in business and not pursuing a baseball career.