Organization: Company A, 1st New York Cavalry
Entered Service: New York, N.Y.
Date Medal Issued: 27 November 1896.
Date of Action: 2 May 1863.
Place of Action: Chancellorsville, Va.
Volunteered to ascertain the character of approaching troops; rode up so closely as to distinguish the features of the enemy, and as he wheeled to return they opened fire with musketry, the Union troops returning same. Under a terrific fire from both sides Lieutenant Thomson rode back unhurt to the Federal lines, averting a disaster to the Army by his heroic act.