In 1804, French Physicists Joseph Louis Gay-Lussac and Jean-Baptiste Biot "made a hot-air balloon ascent to a height of 7,016 metres (23,018 ft)". Gay-Lussac was one of many scientists who contributed to developments of creating sulfuric acid, which was used extensively during the US Civil War...
Take out the Norman Rockwellian characters and I think this is a contender. The characters appear to be composites, they don't match the contrast of the rest of the image (i.e. the missing photograph). This is Crystal Palace, New York, in 1854.
Crystal Palace in New York looked quite amazing...