Samuel Baldwin Marks Young was born in Pittsburgh, Pennsylvania, on 9 January 1840. He attended Jefferson College and then enlisted as a private in Company K, 12th Pennsylvania Infantry in 1861. Soon, he was made a captain in the 4th Pennsylvania Cavalry. In 1861, he married Margaret McFadden. By the end of the Civil War, Young was a brevet brigadier general of volunteers.
In 1866, Young entered the Regular Army as a second lieutenant, and later that year was promoted to captain. Young fought with the 8th Cavalry in the wars against the southwestern Indian tribes from 1866 to 1879. In this time, he was brevetted major, lieutenant colonel and then colonel. By June 1897, Young was a permanent colonel.
During the Spanish-American War, Young was a brigadier general and then a major general of volunteers. He commanded a brigade during the Santiago campaign in 1898. After the war, he led a brigade against the Philippine insurrection from 1899-1901 and then served as the governor of the northern Luzon district. In 1900, Young became a brigadier general in the Regular Army and soon became a major general.
In 1902, Young served as the first president of the Army War College. In 1903, he was promoted to lieutenant general. He served as the first Chief of Staff of the United States Army from 15 August 1903 to 8 January 1904. In the time, he supervised the implementation of the General Staff concept of Army organization. He retired from active service in 1904. Young died in Helena, Montana, on 1 December 1924.
