Only once that I was confident about. In 1972, in the southern Sierra Nevada mountains immediately south of Sequoia National Park, I found a footprint trackway. I moved from California @ 2 years later, and ended up in Southcentral Alaska by late 1975. I don't think southcentral Alaska is their best habitat like areas south of there. I believe that their best habitat is between latitudes 39 degrees and 57 degrees within 100 miles of tidewater.
One other time I heard a very strange knocking sound that, at the time, I believed was a moose that was rapping his antlers against a tree instead of raking it. I'd never heard a moose do that before or since. It was in an extremely remote location in Alaska between the Alaska Range and the Arctic Circle, and we got there via a 700+ mile riverboat trip. My brother actually shot a huge moose in my eyesight while that rapping was going on to my left. I didn't pay attention to whether or not it continued, but a pack of wolves on Billy Hawk Hill, right in front of us, were intermittently howling, and they continued while we began skinning the moose. Night descended on us, and we left the bull laying there half skinned. I worried that the wolves or a bear would come and foul it (I wasn't worried about birds, because they rarely fly in the dark). We arrived back early the next morning before sunrise and found that the moose had not been disturbed. Years later, reading an excellent book on the Native tribe of that area, I found that they describe Billy Hawk Hill as a favored haunt of the woodsman, their name for sasquatches. Of course, I can't say that the knocking was a sasquatch, but it was certainly strange, and it fits with local aboriginal claims.
I am currently looking at various areas that have a strong history of sasquatch reports and legends. I would love to spend several months in such an area "hunting" for a sasquatch. I have no desire to kill one, but I plan to be armed, and will not hestitate for a moment to shoot one if I feel that I'm in danger. Nor do I plan to photograph one, since history shows that photographs prove nothing. I just want to see one.
Many factors are narrowing my chosen location. Canada is out of the question due to their attitudes towards firearms. Southeast Alaska poses significant access difficulties. Even if I got my boat in proper shape for an extended adventure there, it's only 22' long, and it would be a rather tight fit for such a long trip. The Alaska ferry system has a maximun length limit that poses a problem for my truck/camper & trailer.
I'm liking Gifford Pinchot National Forest in Washington and Six Rivers National Forest in northern California. Of the two, California is edging out Washington in every important aspect. The deer hunting is better, and non-resident license and tags are cheaper and easier to get. The fishing is much, much better for steelhead. And there are fewer people to navigate around, especially after deer season ends.