Gideon Welles, (U.S. [Union] Secretary of Navy), one page LS, May 6, 1861 war-date military letter headed 'Navy Department' to Commodore (later Rear Admiral) William Mervine, U.S. Navy, Utica, N.Y., 'Proceed to Boston, Mass. and when the U.S. Steam Frigate 'Colorado' shall be put in commission, you will hoist your flag onboard that vessel...', 7¾ x 9¾" on blue-lined stationery, couple light file folds not affecting signature, very fine