The 264th Engineer Group was organized and Federally recognized as Troop L 1st Cavalry on 17 May 1917 at Eau Claire, Wisconsin. On July 15, 1917 the unit was ordered into active federal service at Camp Douglas, Wisconsin. The unit served in the European Theater of Operations during World War I. The unit was awarded the French Croix de Guerre with Silver Star. 16 May 1919 the unit was demobilized at Camp Grant, Illinois. After the War, the unit was reorganized and redesignated many times and on 15 October 1940 it was inducted into Federal service for World War II as Battery A 173d Field Artillery. The unit again served in the European Theater of Operations playing a key role in four battles. The unit was inactived on 11 September 1945 in Italy. The unit was Reorganized and Federally recognized 30 March 1948 as Battery B 173d Field Artillery. The unit was again called to active Federal service during the Berlin Crisis from 15 October 1961 to 10 August 1962.
In 1988 Wisconsin National Guard combat engineers had their first hands-on training with the new Heavy Expanded Mobility Tactical Truck (HEMTT) at Fort McCoy. Members of the Guard's 264th Engineer Group developed a mine-laying apparatus to use with the new HEMTTs. The Row Minefield Device was designed to allow a squad of six members to lay a deliberate minefield (150 meters deep and 100 meters wide, with 88 mines) in a little more than an hour.
Over the years the unit was reorganized and converted many times and on 1 January 1972 the unit was converted to Headquarters and Headquarters Company 264th Engineer Group located in Eau Claire, Wisconsin. 1 March 1989 the unit was relocated to Chippewa Falls, Wisconsin.
The Associated Press reported on May 12, 2004 that the 264th Engineer Group, consisting of 80 soldiers, was operating in the Middle East. Two of its subordinate units have also been identified as having been activated (by the DoD in its weekly release), but it is unclear how many are with those units or if those units are in Iraq, though they are thought to be.