Pat St. Clair was born on October 13, 1948, in Pearisburg, Virginia. He graduated from Giles County High School in Pearisburg in 1967, and enlisted for the U.S. Army Special Forces in July 1968. St. Clair completed basic training at Fort Bragg, North Carolina, and Airborne Infantry Advanced Individual Training at Fort Gordon, Georgia. He then completed Airborne School at Fort Bragg, and then began Special Forces Training at Fort Bragg in December 1968. After completing Special Forces Training in January 1970, Sgt St. Clair was assigned to Company C, 6th Special Forces Group (Airborne) at Fort Bragg until March 1971. During this time he participated in the Son Tay Raid, a clandestine mission to rescue American Prisoners of War held in North Vietnam on November 21, 1970. He then served with the 5th Special Forces Group (Airborne) at Fort Bragg from March 1971 until his honorable discharge from the Army in July 1971. Sgt St. Clair enlisted in the West Virginia Army National Guard in May 1980, and he served with Company C, 2nd Battalion of the 19th Special Forces Group (Airborne) at Camp Dawson, West Virginia, from May 1980 to October 1994. During this time he served as a medical sergeant, weapons sergeant, intelligence sergeant, operations sergeant, and was promoted to Unit Sergeant Major in 1993. He also served on Mobile Training Teams and on Medical Civil Action Programs missions to South Korea, Thailand, Saipan, Vanuatu, Guam, and the Philippine Islands. After graduating from the Sergeants Major Academy, he served as Post Command Sergeant Major for the State Military Reservation at Camp Dawson, West Virginia, from October 1994 to July 1997, and then as Command Sergeant Major for 1st Battalion, 201st Field Artillery Regiment at Fairmont, West Virginia, from July 1997 to July 2001. CSM St. Clair was next appointed as the first Senior Enlisted Advisor for the newly formed Special Operations Detachment - Europe (SOD-E), headquartered at Camp Dawson, West Virginia, where he served from July 2001 until he was mobilized with his unit to support Operations Enduring Freedom in the Global War on Terrorism. He was selected by the U.S. Army Special Forces to serve as the Command Sergeant Major for the newly formed Support Battalion, 10th Special Forces Group (Airborne) for Operation Iraqi Freedom in November 2002, and was reassigned to the Horn of Africa in May 2003. CSM St. Clair served as the Senior Enlisted Advisor for the Joint Special Operations Task Force-Horn of Africa, from June to October 2003. He served as Command Sergeant Major for the 771st Troop Command, Headquartered in South Ridge, West Virginia, from January 2005 to March 2006, followed by service as the Senior Enlisted Leader for the Training Site Command at Camp Dawson from March 2006 until his retirement from the West Virginia Army National Guard in October 2008.

His Silver Star Citation reads:

For gallantry in action on 21 November 1970 as a member of an all-volunteer joint U.S. Army and Air Force raiding force in the Joint Chiefs of Staff-directed heliborne assault mission to rescue United States military personnel held as prisoners of war at Son Tay prison in North Vietnam. This valiant effort was motivated by deep compassion for his imprisoned fellow men-at-arms, and by a strong sense of military duty and national pride. Sergeant St. Clair was the first man to debark from a helicopter which crash-landed inside the prison compound. Completely disregarding his personal safety, he moved directly to an exposed area and immediately began placing a heavy volume of automatic rifle fire on the fortified northwest guard tower of the prison. He then maneuvered to his next objective where he surprised a number of enemy soldiers. Without hesitation, he courageously attacked the soldiers, forcing them to abandon their fortified positions and retreat into the covering fire of a supporting element of the raiding force. He then calmly and deliberately searched and cleared his assigned area of responsibility. Sergeant St. Clair's courageous actions contributed significantly to the successful execution of the mission, His extraordinary heroism against an armed hostile force, and extreme devotion to duty are in keeping with the highest traditions of the military service and reflect great credit on himself and the United States Army.