He signed the Declaration of Independence in 1776, and later joined with the Continental Army as a physician.
As Surgeon General of the Continental Army, he strongly worked for the health of the soldier. He was with Washington at the Battles of Trenton, Princeton and Brandywine; however, he became discouraged with the conditions of the soldiers and resigned in 1778.
After the American Revolution, he continued his work at the Pennsylvania Hospital. He was a professor at the University of Pennsylvania and wrote the first American book on chemistry. He was appointed as Treasurer of the United States Mint 1797–1813.
Benjamin Rush died April 19, 1813, in Philadelphia, Pennsylvania. He is buried at Christ Church Burial Ground in Philadelphia.