During the second half of the 19th century, America’s cities underwent a dramatic transformation. The big cities of the East were supersized and urban planners raced to keep up. On the other side of the country, new cities grew out of nowhere as the Wild West was tamed. Happily for modern-day history enthusiasts, new photographic technology meant that America’s urban explosion was captured on camera.

Click through this gallery to explore amazing 19th-century photos of American cities, from the Big Apple to the Windy City…