Zouave Passing Through Baltimore
In the early days of the Civil War, Union troops passing through Baltimore had been menaced and in some cases attacked by mobs of pro-Confederacy residents of the city.
This envelope depicted a soldier in a garish Zouave uniform, beside a sign reading "Washington via Baltimore." The soldier, who is holding an American flag, seems to show defiance toward those who were trying to block troops from getting to Washington.
The elaborate Zouave uniforms had been popularized by Col. Elmer Ellsworth in the years just prior to the Civil War. A number of regiments adopted them when going to war in 1861, but their popularity faded quickly. They were not terribly practical to maintain, and it was widely assumed they attracted enemy fire on the battlefield.