[7][8] When the American Civil War started, he was made captain in the Union Army, being in the 4th Artillery under Gen. Nathaniel P. Banks, past Governor of Massachusetts.
[7] Clermont Livingston Best died on April 7, 1897, in New York, at 72 years old, and was buried in Hudson City Cemetery.
[1][8][10] His funeral was attended by General Daniel Butterfield, Mrs. Gabriel Mead Tooker, NYC Police Commissioner Rhinelander Waldo, Mrs. G. Van Cortlandt Hamilton, wife Schuyler Hamilton Jr., great-grandson of Alexander Hamilton, Robert Goelet, brother of Ogden Goelet of Ochre Court, and others.
[10] His son, Clermont Livingston Best Jr., became captain and later major in the US army under Gen. William Montrose Graham during the Spanish–American War.
[11][12] His daughter with Mary Tooker was Annie Livingston Best, who married to socialite Elizur Yale Smith, son of millionaire Wellington Smith, and member of the Yale family.