There are many historical time lines of videoconferencing on the Internet. A nice one is from an earlier post on this very blog. Most of these histories identify the AT&T ikonophone as the first working video phone. Although a milestone in its own right, it was not the first videophone as we think of them today. While the audio was two-way, the video was only one-way.
The first true videophone system, with two-way video and two-way audio, came about in Nazi Germany.