The first documented exhibition of a stereoscopic motion picture took place on the morning of June 10, 1915 at the Astor Theater in New York. Three reels of test footage by Edwin S. Porter and William E. Waddell were presented in red/green anaglyphic 3-D. Shown were rural scenes and footage of Niagara Falls, along with an Oriental dancer and specially-filmed 3-D demo sequences from Jim the Penman with John Mason and The Morals of Marcus with Marie Doro. Shortly after the screening, several articles mentioned blurry images during fast movement. Apparently the footage was shown interlocked on two 35mm projectors that were either out-of-sync or some segments were photographed with the camera shutters severely out-of-phase.
The Astor Theatre is shown here circa 1908.
This test footage does not survive but you can read first-hand accounts in these articles.
On September 27, 1922, the first 3-D feature was previewed at the Hotel Ambassador Theatre in Los Angeles.
THE POWER OF LOVE had one confirmed stereoscopic booking in Newark, NJ and was eventually released flat as THE FORBIDDEN LOVER by Selznick Distributing Corp. on July 28, 1923. It does not survive but the red side of the opening YOSEMITE prologue exists and has just been preserved by the 3-D Film Archive.
More information on the YOSEMITE film can be found here: 3-D Holy Grail
If you have any information on a print of THE POWER OF LOVE or THE FORBIDDEN LOVER, please let us know!