Lt. Col. William B. Guernsey succeeded Col. Silliman on June 18, 1865, and the 26th Regiment was mustered out under his command in South Carolina on August 28, 1865. Notable members include: David Carll, who has a hill in Oyster Bay, NY, named after him; Noah Elliott, the unit's hospital steward, who went on to become the first African American physician in Athens, Ohio; and Benjamin F. Randolph, who as Chaplain was the unit's sole African American commissioned officer, and who was a delegate to South Carolina's Constitutional Convention in 1868.

On December 3, 1863, the United States Department of War authorized the Union League Club of New York to raise one regiment of infantry composed of African Americans.

William Silliman, a captain noted for his heroism at Gettysburg while serving in the 124th New York regiment, was commissioned as commanding officer.

[1] The Regiment was briefly deployed to Annapolis, Maryland, then transferred to Beaufort, SC, Department of the South, on April 13, 1864.

The unit also fought at Chapin's Farm, McKay's Point and Deveraux's Neck, incurring a total of 140 casualties.