The Mutual Base Ball Club of New York was a leading American baseball club almost throughout its 20-year history. It was established during 1857, the year of the first baseball convention, just too late to be a founding member of the National Association of Base Ball Players. It was a charter member of both the first professional league in 1871 and the National League in 1876. The team was initially formed from firefighters of New York's Mutual Hook and Ladder Company Number One. Boss Tweed operated the team until his arrest in 1871.