what is 22nd massachusetts infantry regiment?
It was an infantry regiment in the Union army during the American Civil War.
22nd Massachusetts Infantry Regiment
The 22nd Regiment Massachusetts Volunteer Infantry was an infantry regiment in the Union army during the American Civil War. 
wiki:9175508
22nd Massachusetts Infantry Regiment [SEP] Introduction
The 22nd Regiment Massachusetts Volunteer Infantry was an infantry regiment in the Union army during the American Civil War. The 22nd Massachusetts was organized by Senator Henry Wilson (future Vice-President during the Ulysses Grant administration) and was therefore known as "Henry Wilson's Regiment." It was formed in Boston, Massachusetts, and established on September 28, 1861, for a term of three years. Arriving in Washington in October 1861, the regiment spent the following winter in camp at Hall's Hill, near Arlington in Virginia. It became part of the Army of the Potomac, with which it would be associated for its entire term of service.