USS Modoc, a single turret, an 1,175-ton Casco-class light draft monitor built under contract by J. S. Underhill at Greenpoint, Brooklyn, was completed as a spar torpedo vessel in June 1865. She had no active service, spending her entire Navy career laid up "in ordinary" at Philadelphia. The vessel was renamed Achilles on 15 June 1869, but returned to Modoc on 10 August. The ship was broken up at New York in August 1875.