View of the 1876 Centennial Exhibition, Philadelphia, Pennsylvania

Americans loved stereographs -- millions were made from the mid-1800s through the 1930s. A stereograph consists of two offset photos that appear to have three-dimensional depth when viewed through a stereoscope. These images entertained and educated. Stereographs could transport viewers to faraway places and distant events, like this view of the 1876 Centennial Exhibition in Philadelphia, Pennsylvania.