He was a founder and first treasurer of the American Philosophical Society, one of the first directors of the Philadelphia Contributionship, and an early supporter of Pennsylvania Hospital.
Benjamin Franklin was a close friend of Colman, and said of him, "He has the coolest, clearest head, the best heart, and the best morals of almost any man I ever met."
Coleman was also a founder of the College of Philadelphia (now the University of Pennsylvania, serving as the original clerk of the Board of Trustees, 1749–1755, and as its first treasurer, 1749–1764.
Subsequently, Coleman joined with Franklin to help manage a public lottery held in 1748 to raise funds to cover the costs of building Philadelphia's first military defense, the Association Battery.
[1] In 1756, William Coleman purchased 12 acres of land along the Schuylkill River, where he built an elegant country home which he named Woodford.