Sarj Bloom took this great 1963 panoramic photo of Shihmen Dam, prior to the dam's completion in 1964. He thinks that this may be the only shot of its kind in existence. You can find other historical photos of the dam at the official government website.
Here's the man himself in the process of taking the above shot.
This is a Google image showing the dam's location in relation to TDC.
Sarj also found a link to a YouTube video of the dam in operation today.