Johnston, John Alexander was born on February 22, 1858 in Allegheny, Pennsylvania, United States. Son of Alexander and Sarah R. Johnston.
Graduated from the United States Military Academy, 1879. Honor graduate Infantry and Cavalry School, Fort Leavenworth, Kansas, 1883.
Commissioned Second lieutenant, June 13, 1879. First lieutenant, January 20, 1886. Captain, January 3, 1895.
Major a.a.g., May 19, 1898. Lieutenant colonel a.a.g., February 21, 1901. Brigadier general, January 7, 1903.
Resigned January 15, 1903. Frontier service in Texas, 1879-1882, 1885-1887, in South Dakot, 1891-1893, and 1895-1897. Instructor art of war and engineering, Infantry and Cavalry School, 1883-1885.
Instructor history, law and tactics, United States Military Academy, 1887-1891. In charge mounted instruction, Cavalry Depot, Jefferson Barracks, Missouri, 1893-1895. Duty in office of adjutant general in charge of organization and muster in and out of all volunteer forces raised during Spanish-American War, 1898, and the vols. raised for the Philippines 1898-1901.
In charges reorganization of general recruiting service United States of America, incident to army increase. Prepared reports upon German Army maneuvers, 1902. Was commissioner, District Government, District of Columbia.
Appointed commander Northeastern Department, United States Army, Boston, 1917. Address: Washington, Distric.