Abner Doubleday (1819-1893), Union officer in the American Civil War (1861-1865), born in Ballston Spa, New York and educated at the United States Military Academy. Doubleday served in the U.S. Army during the Mexican War from 1846 to 1848, and in 1861 fired the first gun from Fort Sumter, South Carolina, in response to the Confederate attack at the beginning of the Civil War. He was appointed a brigadier general of volunteers and placed in command of the defenses of Washington, D.C., in 1862, earning promotion to major general in the same year. He continued to serve in the army until his retirement in 1873.

As a young man, Doubleday had organized ball teams in Cooperstown, New York, and there, according to a story that became current after his death but has little support, he devised the diamond-shaped field and the present-day playing positions of the game of baseball.