He joined the Union Army in the first days of the Civil War and rose to commander of the 109th New York Volunteer Infantry Regiment.

Severely wounded during the Battle of the Crater, he remained on the field and led his regiment until he was injured a second time, resulting in the loss of his leg.

[2][4] Tracy, who had married Catlin's sister Delinda in 1851, would also earn the Medal of Honor in the Civil War and would go on to become United States Secretary of the Navy.

[1][4] Immediately after President Abraham Lincoln's call for volunteers at the beginning of the Civil War, Catlin raised a company of infantry and was appointed its captain.

The unit, said to be "the first full company which enlisted in the North," was mustered in on May 14, 1861, as part of Frederick Townsend's 3rd New York Volunteer Infantry Regiment.

Regarding the regiment's participation in the Battle of Big Bethel on June 10, 1861, Townsend remarked: "There was no braver officer on that field than Captain Catlin.

For this action, he was given a brevet promotion to major general on March 13, 1865, and awarded the Medal of Honor several decades later, on January 13, 1899.

[3] Catlin's official Medal of Honor citation reads: In a heroic effort to rally the disorganized troops was disabled by a severe wound.

He was elected the district attorney of Tioga County in 1865 and six years later, in 1871, formed a law partnership in Brooklyn with his brother-in-law, Benjamin F. Tracy.