William Tilghman, a cousin of Edward Tilghman Jr., was born on 12 August 1756 in Talbot County, Maryland. A graduate of what is now the University of Pennsylvania, he was a loyalist during the American Revolution, and was paroled to his plantation for a time.  Following admittance to the Maryland bar in 1783, he served in both houses of that state's legislature. In 1794 Tilghman returned to Philadelphia, where he practiced law, sat in the U.S.