[2] The unit was one of four Massachusetts militia regiments to respond to Abraham Lincoln's call for 75,000 volunteer troops after the Battle of Fort Sumter on April 15, 1861.

Three companies of the 8th Massachusetts earned the distinction of being the first troops to report to Boston, arriving less than a day after the call.

During their first "90 days" term, the regiment mainly served garrison duty in the vicinity of Elkridge, Maryland, repairing and guarding the railroad line between Washington, D.C., and Baltimore.

Shortly after arriving in Maryland, the regiment briefly occupied the United States Naval Academy, securing that installation and the USS Constitution, both of which were believed to be in danger of capture by Confederate troops.

[3] Many members of the regiment enlisted in the 19th Massachusetts Volunteer Infantry after their return to the Commonwealth in July.