Stereoscopes were the first mass-produced viewers for three-dimensional (3-D) photography. Stereoscopes allowed people to view two photographs of a single scene taken from slightly different perspectives (called stereographs) as one 3-D image. The 3-D images brought a realism and a depth to photography that had never before been seen.

The stereoscope, pictured here circa 1870, was the first device that allowed people to view 3-D images. Hulton/Archive. Reproduced by permission.

Stereoscopy, popular from 1850 to 1920, was a forerunner of cinema and television (see entry under 1940s—TV and Radio in volume 3). From the comfort of their own homes, people could use the stereoscope to see images of important people, places, and historic events. The device also enabled them to entertain themselves with erotica (pictures meant to arouse sexual interest), images of tourist destinations, and fine works of art. Invented by British physicist Charles Wheatstone (1802–1875) in 1832, the stereoscope truly became...