Army officer, business and political leader, and civic activist. Clarkson joined the Continental Army at the start of the Revolution and served under Benedict Arnold and Benjamin Lincoln, rising to the rank of lieutenant colonel. When Lincoln was Secretary of War from 1781 to 1783, Clarkson served as Assistant Secretary. An anti-slavery activist, Clarkson served in the New York Assembly from 1789 to 1790, and introduced a bill calling for the gradual abolition of slavery, a goal New York achieved in the 1820s. He continued to hold office and was also a civic activist, serving as a Regent of the University of the State of New York, US Marshal, New York Senator, member of the commission that built New York's first state prison, President of the New York City Hospital, and Vice President of the American Bible Society. He was a longtime vestryman of Trinity Church. For more than twenty years Clarkson was President of the Bank of New York, and he was also a successful investor and land speculator. Clarkson donated much of his wealth to support his civic and religious causes. He also continued his military service, commanding the state militia in New York City and several surrounding counties with the rank of major general, a position he held for more than fourteen years. Clarkson Street in New York City was named for him, as was the town of Clarkson in New York's Monroe County.

Army officer, business and political leader, and civic activist. Clarkson joined the Continental Army at the start of the Revolution and served under Benedict Arnold and Benjamin Lincoln, rising to the rank of lieutenant colonel. When Lincoln was Secretary of War from 1781 to 1783, Clarkson served as Assistant Secretary. An anti-slavery activist, Clarkson served in the New York Assembly from 1789 to 1790, and introduced a bill calling for the gradual abolition of slavery, a goal New York achieved in the 1820s. He continued to hold office and was also a civic activist, serving as a Regent of the University of the State of New York, US Marshal, New York Senator, member of the commission that built New York's first state prison, President of the New York City Hospital, and Vice President of the American Bible Society. He was a longtime vestryman of Trinity Church. For more than twenty years Clarkson was President of the Bank of New York, and he was also a successful investor and land speculator. Clarkson donated much of his wealth to support his civic and religious causes. He also continued his military service, commanding the state militia in New York City and several surrounding counties with the rank of major general, a position he held for more than fourteen years. Clarkson Street in New York City was named for him, as was the town of Clarkson in New York's Monroe County.