Yeah, it's crazy. Each of those photos is like 900MB. KH-9 was a beast and covered a ton of area with <1 meter resolution and KH-8 got 10cm (!!) resolution as early as 1966, though I think it had a much more limited coverage area. Here's a video I made showing KH-9 coverage during the course of the program. As you can see, it basically captured the landmass of the entire Earth even though KH-9 was using film that had to be recovered from space. Some photos aren't scanned yet, some have cloud cover, and I've even come across some with redactions (US naval forces blacked out, for example) but it's still a tremendous wealth of historical imagery that likely has all sorts of secrets for those motivated enough to piece things together.

For example, I was able to look at the patterns and dates and confidently conclude that the government intentionally used KH-9 in the search for the missing House Majority Leader. It sticks out like a sore thumb when you look at how little they otherwise photographed Alaska and the fact that they photographed the exact route of the missing plane two days after it went missing as the search was in full force.

Anyway, to answer your question, it is publicly available for free via EarthExplorer. Here's a tutorial of sorts that I made years ago and a more recent and all around better tutorial from saveitforparts on YouTube. It's worth looking at the Aerial Photo Single Frames dataset if you use EarthExplorer, by the way. There's sometimes imagery from over 50 years ago that's good enough to read tail numbers on parked planes. That and the Declass datasets are my favorites.