National Archives – St. Louis: Military Personnel Records (Order Form and Contact Information) These include Officers separated after June 29, 1917. Enlisted personnel separated after October 31, 1912. Many records were destroyed by fire in the St. Louis Center in 1973.
National Archives – Washington DC: Military Service Records, Pensions, and Bounty Land Warrants (Order Form and Contact Information) These include Volunteers, Army, Navy, Marine Corps, Coast Guard, Confederate States, Pensions, Bounty Land Warrants 1775-1919. Specific itemization of available records may be studied on the linked site.