The 55th Massachusetts Infantry Regiment was the sister regiment of the renowned Massachusetts 54th Volunteers during the latter half of the American Civil War. The enactment of the Emancipation Proclamation by United States President Abraham Lincoln on January 1, 1863 opened the way for the enlistment of free men of color and newly liberated slaves to fight for their freedom within the Union Army. As the ranks of the 54th Massachusetts quickly reached its full complement of recruits, an overflow of colored volunteers continued to pour in from several other states outside Massachusetts — many of whom simply had not arrived in time — prompting Governor John Albion Andrew to authorize yet another regiment of colored soldiers sponsored by the Commonwealth. Lieutenant Colonel Norwood P. Hallowell of the 54th Massachusetts was promoted to colonel and appointed commander of the 55th Massachusetts on May 30, 1863. Five companies of the 55th Massachusetts were mustered into service on May 31; two more companies were mustered in on June 15; and the last three on June 22.

The 54th Massachusetts Infantry Regiment was an infantry regiment that saw extensive service in the Union Army during the American Civil War. The unit was the second African-American regiment, following the 1st Kansas Colored Volunteer Infantry Regiment, organized in the Northern states during the Civil War. Authorized by the Emancipation Proclamation, the regiment consisted of African-American enlisted men commanded by white officers. The 54th Massachusetts was a major force in the pioneering of African American civil war regiments, with 150 all black regiments being raised after the raising of the 54th Massachusetts.