Part of a series of 22 plaques surrounding Union Square depicting the history of the square from 1600 to 1882 - the year in which the first Labor Day Parade took place at Union Square, and labor movement events that were held in the United States (Union)
The plaques are made of bronze, designed by Gregg LeFevre and set up in 2002
Raising the flag for the Afro-American 20 regiment that fought alongside the northern states during the civil war. The ceremony took place on March 5, 1864
The 20th U.S. Colored Infantry was, as mentioned, a battalion consisting of African-American soldiers, but its commanders were white. The regiment formed in May, 1863, operated slightly over two years and closed in October, 1865.
"Presentation of Colors" - is a ceremony marking an event in the history of a military unit, a ceremony originating in the United Kingdom.
The ceremony took place at The Union League Club which was at 26 East 17th Street facing Union Square.
The plaque is identical to the one that appeared in the Frank Leslies Illustrated Newspaper on 26 March 1864.
See the photo on the New York Public Library website: Presentation of Colors to the 20th U.S. Colored Infantry