Perceived as a threat to the security of the United States, he was jailed briefly in 1778 by order of Congress, and then imprisoned again in 1780.
[2] From 1771 to 1781, he owned and occupied Woodford, a mansion in Germantown, now a National Historic Landmark, to which he added a second story and a rear two-story addition.
By various accounts, Franks died in the Yellow Fever Epidemic of 1793 in Philadelphia,[4][5] where he was buried in Christ Church Burial Ground.
His nephew, Col. David Salisbury Franks, a revolutionary who served as aide to Benedict Arnold, came under further suspicion because of his relationship with his loyalist uncle.
His youngest daughter, Rebecca, became the wife of then British colonel (later General) Henry Johnson, and was one of the prominent young Philadelphians who attended the Mischianza Ball.