In 1780, he was one of three men to capture British Major John André, who was convicted and executed as a spy for conspiring with treasonous Continental general and commandant of West Point Benedict Arnold.
Despite this condition, Williams continued to lend his support to the volunteer forces in his native area: overnight on September 22–23, 1780, he joined militiamen John Paulding and Isaac Van Wart as part of an armed patrol.
The three militiamen were highly celebrated in their lifetimes: commemorations large and small abound in Westchester (see below), and can be found in many disparate parts of the early United States.
André at his trial had insisted the men were mere brigands; sympathy for him remained in some more aristocratic American quarters (and grew to legend in England, where he was buried in Westminster Abbey).
Giving voice to this sympathy, Representative Benjamin Tallmadge of Connecticut persuaded Congress not to grant the men a requested pension increase in 1817, publicly assailing their credibility and motivations.
Some modern scholars interpreted the episode as a major event in early American cultural development, representing the apotheosis of the common man in the new society, even if that means both ignoring contemporary accounts of their character and actions and subsequent inflation of both during the nineteenth century.