Rev. James K. Ewer , Company 3, Third Mass. Cav., Roster of the Third Massachusetts Cavalry Regiment in the war for the Union

[503] the making of a complete Roster of the Third Massachusetts Cavalry meets with difficulties greater than those connected with most other regiments. The Forty-first Massachusetts Volunteer Infantry left the State on November 5, 1862, with eight companies and seven hundred men. In Baton Rouge, two companies from the Thirty-third Massachusetts Infantry were added, ‘I’ and ‘K.’ On June 17, 1863, while in Louisiana, the regiment was converted into the Third Massachusetts Volunteer Cavalry, and other companies that had preceded them with Butler's Expedition were added, the First, Second and Third unattached companies. These were added as Companies ‘L,’ ‘M,’ and Read's Company. On March 26, 1865, Colonel Burr Porter joined the regiment and assumed command. With him, certain detachments of troops that had been recently recruited in the State were received and merged with Companies ‘L’ and ‘M’ By the addition of these different companies, and by the recruits received from time to time, the rolls were increased to over twenty-five hundred men.

On May 20, 1865, the original members of the regiment were mustered out of service. On July 21, those remaining were, by order of the War Department, consolidated into six companies, in which position they continued until September 28, 1865, when the entire regiment was mustered out of service. Because of these changes, the same person may have been at different times a member of more than one company.

There is no complete Roster, arranged alphabetically by companies, at the Adjutant General's office of the State, but there are records compiled from the muster rolls of the regiment, together