William Grafton Austin was born on January 6, 1868 in Grimes County or Galveston, Texas. He enlisted in E Troop, 7th Cavalry Regiment of the U.S. Army in New York City on January 24, 1887; his age is recorded as 24 (birth year 1862 or 1863). He fought in the Battle of Wounded Knee on December 29, 1890 and was awarded the Medal of Honor on June 17, 1891 for actions "while the Indians were concealed in a ravine, assisted men on the skirmish line, directing their fire, etc., and using every effort to dislodge the enemy". He was discharged as a sergeant on January 23, 1892 at Fort Riley, Kansas.