Colonel St. Clair was born in Baltimore, Maryland. After graduation from The Virginia Military Institute in 1989 with a Bachelor of Arts in History, he was commissioned into the Marine Corps and trained as an infantry officer. He holds a Master of Airpower Art and Science degree and a Master of Strategic Studies degree.
From April 1990 - April 1993, Colonel St. Clair served as a rifle and weapons platoon commander with 2d Battalion, 8th Marines, deploying with the 24th Marine Expeditionary Unit. Upon return he served as the battalion adjutant and as a rifle company executive officer deploying to Okinawa, Japan.
From April 1993 - December 1995 Colonel St. Clair was assigned to The School of Infantry (East) where he held billets as the commanding officer, Company B, Infantry Training Battalion and as the School S-3 assistant operations officer. Upon completion of the U.S. Army Armor Officer Advanced Course at Fort Knox, Kentucky in June 1996, Colonel St. Clair assumed command of Company D, 2d Light Armored Reconnaissance Battalion, 2d Marine Division.
From December 1997 to June 1999 Colonel St. Clair served as the assistant operations officer, 22d Marine Expeditionary Unit. In July 1999 he was assigned to the Marine Corps Recruit Depot, Parris Island, South Carolina where he served as the battalion executive officer, 2d Recruit Training Battalion and Director, Drill Instructor School until June 2002.
Following completion of the U.S. Air Force School of Advanced Air and Space Studies in July 2003, Colonel St. Clair was assigned to the 4th Marine Expeditionary Brigade (Anti-Terrorism), II Marine Expeditionary Force where he held billets as the G-3 future plans and current operations officer and commanded an Anti-Terrorism Task Force deploying to the U.S. Embassy, Kabul, Afghanistan (2004). He also led an Advisor Support Team to Fallujah, Iraq (2004-2005) and one to Baghdad, Iraq (2005) serving as the senior advisor to two Iraqi infantry battalions.
In June of 2006 Colonel St. Clair was assigned as a G-3 future plans officer, 2d Marine Division until taking command of 3d Battalion, 8th Marine Regiment in October 2006.
Following a deployment as the Ground Combat Element for the 22d Marine Expeditionary Unit, he was re-assigned as a G-3 training officer, II Marine Expeditionary Force. Colonel St. Clair graduated from the U.S. Marine Corps War College in 2009 and was assigned as a Military Assistant to the Executive Secretary, Office of the Secretary of Defense, Department of Defense.
From June 2011to June 2014 Colonel St. Clair commanded the 26th Marine Expeditionary Unit and deployed to the 5th Fleet Area of Operations. Colonel St. Clair assumed his current position as the Commander, Ground Combat Element Integrated Task Force in June 2014.
Colonel St. Clair’s awards include the Defense Superior Service Medal, Legion of Merit, Bronze Star Medal, the Meritorious Service Medal w/2 gold stars, the Navy and Marine Corps Commendation Medal with 1 gold star, and the Combat Action Ribbon.
Colonel St. Clair is married to the former Melissa Whiteford of Whiteford, Maryland.