The history of Camp Humphreys dates back to the beginning of the 20th century when, in 1919, the Japanese military built the Pyeongtaek Airfield. Later, during the Korean War, Pyeongtaek Airfield was named K-6 after being repaired and enhanced by the U.S. Air Force to accommodate a U.S. Marine Air Group and the 614th Tactical Control Group.

Camp Humphreys

In 1962, the base was renamed Camp Humphreys, in honor of Chief Warrant Officer Benjamin K. Humphreys, a pilot assigned to the 4th Transportation Company, who died in a helicopter accident.

In 1964, Humphreys District Command (later re-designated as the 23rd Direct Support Group) was activated as a separate installation command of the Eighth U.S. Army, providing all direct support, supply and maintenance, storage of all conventional ammunition in Korea, Adjutant General publications and training aides and the Eighth U.S. Army Milk Plant.

USAG Humphreys

In 1974, with the activation of the 19th Support Brigade, Camp Humphreys was re-designated as U.S. Army Garrison, Camp Humphreys. USAG-Camp Humphreys was still responsible for all affairs affecting personnel stationed at Camp Humphreys, but the 19th Support Command was responsible for all support activities vital to the Eighth U.S. Army and its subordinate units. Those units formerly reporting to the 23rd Direct Support Group, reported to the 19th Support Command in Daegu. Only the basic functions remained with USAG Camp Humphreys.

Later, the 23rd Direct Support Group and 19th Support Group were renamed 23rd Support Group and 19th Theater Army Area Command. On 17 June 1996, the United States Army Support Activity Area III (USASA Area III) was established and made responsible for the peacetime support mission for Camp Humphreys, Camp Long, Camp Eagle and U.S. Army units assigned to Suwon Airbase.

On 1 June 2005, the U.S. Army announced that Camps Eagle and Long would close. Both camps were then later closed on 4 June 2010, consolidating installation support activities on
Camp Humphreys.

Under a 2004 land-swap agreement, the U.S. promised to gradually return a combined 170 square kilometers of land, housing 42 military bases and related facilities, to South Korea and move U.S. military forces from garrisons in and north of Seoul to Camp Humphreys.

With the creation of the Installation Management Command on 24 October 2006, U.S. Army Support Activity Area III was re-designated as U.S. Army Garrison Humphreys and Area III, on 15 March 2007.

On 13 November 2007, USFK and South Korean officials conducted a groundbreaking ceremony for the expansion of Camp Humphreys. Under that plan, the 28,500 U.S. troop presence in South Korea will be consolidated into two regional hubs in Pyeongtaek and Daegu.