The 47th Massachusetts Infantry Regiment trained at Camp Edwin M. Stanton in Boxford, Massachusetts and Camp Meigs in Readville, Massachusetts. On November 29, 1862, they left Boston for New York City where troops were being gathered to reinforce the Army of the Gulf under Major General Nathaniel P. Banks. On December 21, 1862, the regiment boarded a steamship for and reached New Orleans on December 31. The regiment was initially stationed at the United States Barracks, the former headquarters of the Louisiana State Guard. In January 1863, several companies of the unit were detached and ordered to serve guard duty at various locations in New Orleans.
On March 12, 1863 all but one of the companies (Company B), were recalled and the regiment went into camp at Metairie Race Course. The location had been converted into a military camp by the Confederates prior to the capture of New Orleans by the Admiral David Farragut. The location was described as extremely unhealthy. Colonel Marsh was given command over the camp and the several units there. He worked to put the site into better order and also focused on improving the 47th Massachusetts in drill and discipline. During their time at Metairie, companies were detached periodically for brief reconnaissance missions closer to Confederate positions. One company encountered Confederates at Amite River on April 17, 1863 and a brief skirmish followed with no casualties. Another company was involved in a larger engagement, the Battle of LaFourche Crossing on June 20, 1863, but did not suffer any casualties.
On May 19, 1863, the regiment was ordered to Camp Parapet, about two miles up the Mississippi River from New Orleans. Colonel Marsh took command of the post. Since the Union's occupation of the area in 1862, Freedmen had gathered at Camp Parapet in large numbers seeking protection of the Union Army. They were organized into "colonies" or camps. While in command of the post, Colonel Marsh oversaw the organization of the 2nd Louisiana Engineer Regiment, a unit composed of African-American volunteers.