One of the rivers I fished is the Firehole River, or as it's less commonly known, Gonorrhea Creek.
Only got one night on it, and had kind of a weird size distribution. I was dry flying it, and there

was non stop action of small stuff in the 5-8 inch range, browns and rainbows. There were two exceptions, a couple rainbows that were approx 14 and 16 inches respectively. I only fished there one night so I don't know if that's typical or not. Don't have any fish pics as I'm leery of wading with a digital camera, and on that stretch of the Firehole it's flies only, and you have to release anything over 13 inches.
First pic is me and the girls with a section of the Firehole in the backgrond called the Keppler Cascades.
Second pic is a little ways downstream of the Keppler Cascades, and a few miles upstream of Old Faithful. Shown is the start

of the section I fished. Picture is taken from a bridge, and it's fairly easy access to the river from the bridge. Upstream of the bridge is flies only, downstream of the bridge towards Old Faithful is no fishing at all due to the high number of hot springs close to or in the river.

Last pic shows how the river got it's name. There's a ton of hot springs that empty directly into the river, and fishermen have died falling into them.