He was an eighth generation descendant of Plymouth Colony militia commander Captain Myles Standish.

During the Spanish–American War, Slocum was commissioned as major in the Inspector General branch in May 1898 and reverted to his permanent rank of captain a year later.

Slocum was exonerated for his failure to prevent the attack by a board of inquiry led by United States Secretary of War Newton Diehl Baker, Jr. [2] Solcum remained on active duty with the Army through World War I and retired from the Army when he reached the mandatory retirement age of 64 on April 25, 1919.

Colonel Slocum died on March 29, 1928, in Washington, DC and is buried in Arlington National Cemetery.

[1][3][4] Colonel Slocum was a hereditary member of the Military Order of the Loyal Legion of the United States, the Order of the Indian Wars of the United States, the Society of Colonial Wars and the General Society of Mayflower Descendants.