View of Zouaves and other soldiers during a parade along Broadway in Baltimore, Maryland, c. 1860s. Attributed to photographer William Chase. The wagon seen at right is possibly a military one. Originally published as a stereoview. NYPL dates this photo to 1880, but I think it was taken much earlier.
Update: Posts by Ross Kelbaugh and Ron Field on Facebook seem to date this photo to 1867 or 1868. The 6th Maryland Regiment is wearing the Zouave uniforms while the 5th Maryland Regiment (visible in the distance) is wearing gray uniform.