Rathbone, an insurance executive and volunteer firefighter in New York, was the sergeant major of his militia regiment. On April 19, 1861, four days after Lincoln called for the states to assemble 75,000 militia, the regiment left New York for Washington to be mustered into federal service. In June, Rathbone and his regiment returned to New York. The regiment was called into federal service two more times during the war in 1862 and in 1863.