Later that year, Franklin married Elizabeth Downes on 4 September 1762 at St George's, Hanover Square, in London. She was born in the English colony of Barbados to the sugar planter John Downes and his wife, Elizabeth (). She met Franklin while visiting England with her father in 1760. They moved to the New Jersey colony in 1763. Elizabeth died in 1777 while he was imprisoned as a Loyalist during the American Revolutionary War. She was interred beneath the altar of St. Paul's Chapel in lower Manhattan, where she had resided after the British evacuated Perth Amboy. The memorial plaque on the wall at St. Paul's was commissioned by William Franklin from London, where he went into exile following the war. He was a widower for more than ten years.