Cathy (or Cathay) Williams (1844 - 1892) was the first recorded African American female to serve in the United States Army.
On November 15, 1866, Cathy Williams decided to enlist, and joined up with the United States Regular Army in St. Louis, Missouri. Being relatively tall (5'9") and physically tough after many years of forced marches and hard physical labor, Williams apparently had no problem passing a cursory physical exam. She initially signed on for a three-year tour of duty under the name "William Cathay."
Read more about Cathy Williams here.
Text Attribution: Wikipedia