In the 1830s, Sir Charles Wheatstone developed stereoscopy, which is a technique that uses two slightly different images, one seen by the right eye, and the other by the left, to create a three-dimensional experience for a viewer. His stereoscope used mirrors and drawings, but it was large and bulky. Over the next half-century, many improvements were made. David Brewster created the first model with lenses, allowing for a smaller original image and therefore a smaller apparatus. This model was exhibited at the Great Exhibition of 1851 and became a favorite of Queen Victoria. The trend caught on, and in the late 1850s, Oliver Wendell Holmes, Sr., developed a hand-held model which was much more affordable, allowing any middle-class household to own a stereoscope.
The subject of stereo cards ran the gamut. Images of travel were popular, like this example from Niagara Falls.
Images of events were also in high demand. This image may have been from a US Centennial celebration.
Hometown scenes, many times of family or residences, were also of interest. This card shows the Court House in Norristown.
And certainly the most fun theme was the pun or joke stereo card, as seen with these fashionable cats.
You didn’t really think Grumpy Cat was the first feline beloved by the American public, did you?