Estes received the country's highest award for bravery during combat, the Medal of Honor, for his action at Flint River in Georgia on August 30, 1864.

He joined the 1st Maine Volunteer Cavalry Regiment[3] as a first sergeant in October 1861, and was commissioned as first lieutenant in March 1862.

Part of the advance party that reached the Atlantic coast, Estes was the first to contact the Union naval forces waiting offshore.

[5] By the time he mustered out in September 1865 at the age of 21, he was a major, and had received a brevet promotion to brigadier general.

[6] After contracting pneumonia, he died from heart failure at his home in Washington, D.C. on February 21, 1905, and his remains are interred at the Arlington National Cemetery in Virginia.