You’ve seen this picture a hundred times.

It appears in almost every book and article about African Americans serving in the Union Army, and on blogs dedicated to the subject. I’ve even used it here, myself. It’s an image of Company E, 4th U.S. Colored Infantry. I’d always guessed that this image was taken early in the 4th’s history, perhaps during its training phase; the uniforms and equipment (including polished shoulder scales) seemed too pristine, too precisely-placed (below). These are, I decided, garrisoned soldiers, not men who’ve been spending their time recently on the march or living in the field.

My reasoning was right, but my conclusion about the date was wrong. The image was not made during the 4th USCT’s working-up period. On the upper edge of the full image, available from the Library of Congress, the notation is scratched on the glass plate negative reads…