the unit was ordered into active service for the defense of washington on 19 april 1861 with attached companies from the 1st and 7th regiments of infantry, massachusetts volunteer militia, and major cook's light artillery company. it was mustered into federal service on 1 may 1861 at washington, d.c., for three months service, and assigned to the 1st brigade, 3rd division. it participated in the first battle of bull run before being mustered out on 1 august 1861 at boston. the unit was again mustered into federal service between 16 september – 8 october 1862 at wenham for nine months service; during which time it served in the department of north carolina and with the xviii corps. it was mustered out on 2 july 1863 at wenham. it was mustered into federal service at camp meigs, readville, massachusetts, in july 1864 for 100 days service and served with the viii corps in the middle military division (baltimore and vicinity) before being mustered out on 16 november 1864 at readville and resumed state militia status as the massachusetts volunteer militia.