http://www.29thdivisionassociation.com/121%20Engineer%20Battalion%20history.html
Taken from this link:
The 121st Engineer Battalion continued its training program at Fort Meade until 10 April 1942. On this date the battalion, less 5 officers and 180 men, was transferred to Indiantown Gap, Pennsylvania, and redesignated the 117th Engineer Battalion, organic to the 37th Infantry Division.
More history taken from a book on the 121st...
HISTORYThe battalion was created in 1918 in the District of Columbia National Guard. It was mobilized into Federal service in 1940 as part of the 29th Infantry Division, made up of units from Maryland, Virginia, and the District of Columbia. The 121st staged at Fort Meade, Maryland for movement to England. At the same time, the 37th Infantry Division from the Ohio National Guard, was staging at Fort Indiantown Gap, Pennsylvania.
The 37th has also been alerted for movement to England, and had sent its 112th Engineer Combat Battalion ahead as part of the advance party. Orders were changed and the 37th was diverted for service in the Pacific Theater. There was no time to recall the 112th, or to create and train a new engineer battalion. The War Department ordered all personnel and equipment of the 121st Engineers moved from Fort Meade to Fort Indiantown Gap, and the unit was redesignated the 117th Engineer Combat Battalion. One officer and six enlisted personnel, symbolically representing the 121st Headquarters, each line Company, and the Medical Detachment, remained behind with the organization's colors.
The new 117th Engineers shipped out to the Fiji Islands, and saw extensive combat in the Philippines. The men from the DC Guard worked under enemy fire building and repairing 64 bridges, destroying enemy held buildings and tank obstacles, and participating in river crossings with "consummate skill and courage."
When the 29th Division reached England, the 112th Engineer Battalion from the 37th Division became the reconstituted 121st Engineers. By the time the 121st saw its first combat, on D-Day at Omaha Beach during the invasion of Normandy, its ranks consisted of the soldiers from Ohio as well as new soldiers from throughout the United States. None of the seven original DC Guardsmen were with the unit at the time of the invasion.
The battalion remained active until May 1945 in operations throughout Europe.
The history, lineage and honors of the 121st continue today in the lineage of the 372d MP Battalion of the District of Columbia Army National Guard. In 1948, a "new" 121st Engineer Battalion was established in the Maryland Army National Guard. Although it carries the same name as the WWII unit, the new MDNG unit has NO previous history.