The regiment moved to Relay House on the Baltimore and Ohio Railroad where additional companies (E, F, G, H, I and K) were mustered between May 25 and May 27.

[1] While recruiting in the streets of Baltimore they hung a flag with the inscription "Recruiting office for the First Maryland Avengers.”[2] The regiment's first commanding officer was Colonel John Reese Kenly, a Baltimore attorney who had served in Mexican–American War as a major of volunteers.

When Kenly was promoted to Brigadier Genreral in August 1862, the new regimental commander was Colonel David Leroy Stanton.

The regiment was stationed at Front Royal on May 23, 1862, when it was attacked by Maj. Gen. Stonewall Jackson's Army of the Valley.

According to J. J. Goldsborough, who would go on to write the history the Maryland Line in the Confederate Army: nearly all recognized old friends and acquaintances, whom they greeted cordially, and divided with them the rations which had just changed hands.