After the Revolutionary War, Wickham earned a degree in law from the College of William and Mary, where he became a close friend of John Marshall, later fourth Chief Justice of the U.S.. Wickham moved to Richmond and experienced tremendous financial success helping British merchants collect debts from American businessmen. He married his first cousin Mary Smith Fanning and had two children. After her early death, he married Elizabeth Seldon McClurg and had seventeen more children. McClurg was the daughter of Dr. James McClurg, Richmond Mayor, U.S. Congressman, and a delegate to the Philadelphia Convention, which framed the Constitution of the United States in 1787.