When Barnum and Bailey’s “Greatest Show on Earth” rolled into American towns in the 1880s, daily life abruptly stopped. Months before the show arrived, an advance team saturated the surrounding region with brilliantly colored lithographs of the extraordinary: elephants, bearded ladies, clowns, tigers, acrobats, and trick riders.

On “Circus Day” (as it was known), huge crowds gathered to observe the predawn arrival of “herds and droves” of camels, zebras, and other exotic animals—the spoils of European colonialism. Families witnessed the …