These are scans of stereoscopic image cards. The kind that are used in the old-fashioned stereoscope viewers. Click through the images to Flickr, if you want to see them bigger (except for the first). The cards that were dated, were dated from 1904 to 1906. A couple of them were published by the Barnes-Crosby Co., Chicago.
I've reversed the images from side to side, so that you can see them without the viewer. Cross your eyes until the two images completely overlap in the center. While keeping the images fused, let your eyes focus on the image, so that the details become sharp. If you can do this, you will be able to see this scene in three dimensions. If you're having trouble, relax your eyes, so the two blurry images float around lazily. Eventually, they'll overlap - try to hold them there. Then wait until the overlapping images pop into focus.

Old Soldiers' Home, Milwaukee, Wisconsin

Steps leading to the Kiyomizu Temple at Kyoto, Japan

Rothesay, Scotland

First Communion

Palace of Fredericksborg, Denmark

The White Tower, Tower of London, England

Magnificent St. Peter's, Rome, Italy

Frankfort on Main, Germany

Rhine Country Mountain

Winter in the Candian Rockies, Banff, Canada

Hudson River

The Narrows, Lake George
I've reversed the images from side to side, so that you can see them without the viewer. Cross your eyes until the two images completely overlap in the center. While keeping the images fused, let your eyes focus on the image, so that the details become sharp. If you can do this, you will be able to see this scene in three dimensions. If you're having trouble, relax your eyes, so the two blurry images float around lazily. Eventually, they'll overlap - try to hold them there. Then wait until the overlapping images pop into focus.

Old Soldiers' Home, Milwaukee, Wisconsin

Steps leading to the Kiyomizu Temple at Kyoto, Japan

Rothesay, Scotland

First Communion

Palace of Fredericksborg, Denmark

The White Tower, Tower of London, England

Magnificent St. Peter's, Rome, Italy

Frankfort on Main, Germany

Rhine Country Mountain

Winter in the Candian Rockies, Banff, Canada

Hudson River

The Narrows, Lake George