Fifteen Massachusetts infantry regiments, one cavary regiment, three batteries of artillery and two companies of sharpshooters fought at the Battle of Antietam. All are honored on the State of Massachusetts monument, and three of the infantry regiments have individual monuments as well.

The State of Massachusetts monument on the Antietam battlefield State of Massachusetts
Irish Brigade monument on the Antietam battlefield Irish Brigade
(29th Massachusetts and
63rd, 69th and 88th New York)
 Monument to the 15th Massachusetts Volunteer Infantry Regiment on the Antietam battlefield 15th Massachusetts Infantry Regiment
Monument to the 39th Massachusetts Volunteer Infantry Regiment on the Antietam battlefield 21st Massachusetts Infantry Regiment  Monument to the 35th Massachusetts Volunteer Infantry Regiment on the Antietam battlefield 35th Massachusetts Infantry Regiment