The unit was first formed in September 1862 in response to President Abraham Lincoln's call for 300,000 men to serve for nine months.

[2] The regiment was assigned to the Army of the Gulf commanded by Major General Nathaniel P. Banks and saw action in Texas and Louisiana.

Company K was assigned to the engineering department of the XIX Corps and carried out bridge building and the removal of naval mines in various waterways.

[3] The 42nd Massachusetts enlisted for a second term of service in response to the call for volunteers to serve 100 days in the defense of Washington.

They performed garrison and picket duty in Alexandria, Virginia and Great Falls, Maryland and were mustered out of service on November 11, 1864.