3-D technology has been around in one form or another for a very long time. It was fairly common even around the time of the Civil War, in what were known as stereoview pictures -- two photos of the same scene taken from slightly different perspectives (that difference corresponding, more or less, to the distance between your right and left eye) that, when viewed together with a stereoviewer, would trick your brain into resolving the two pictures into a single 3-D image. The stereoview cards looked like this:

They were mass-produced and are still pretty common at antique shops and such, but few people have stereoviewers, so it's tough to get a sense of what the 3-D image would look like -- especially on the web. But by animating a gif to quickly alternate between the left and right view, you can get an approximate sense of what the 3-D is like. The Smithsonian recently posted some animated gifs of stereo cards from their collection, and they're fascinating. At the risk of wigging out some of our readers with its constant flicker, here's a shot of a jaunty-looking officer posing by his tent:

There are many more Civil War-era 3-D "motion pictures" on NPR's Picture Show blog.