The 21st Engineer Regiment is a unit within the United States Army, specialized in engineering operations and services. Primarily based at Fort Drum, New York, this regiment forms part of the I Corps and is tasked with providing mobility, countermobility, survivability, and general engineering support to other military units. The 21st Engineer Regiment's responsibilities encompass various aspects such as bridging, demolitions, road construction, airfield construction and maintenance, and mapping. The regiment also provides emergency services, disaster response, and humanitarian assistance when necessary. Throughout its history, the 21st Engineer Regiment has taken part in numerous significant military operations, including the Gulf War, Operation Enduring Freedom, and Operation Iraqi Freedom.