Anyone know about the Gallatin river?

You may want to skip the upper Gallatin in Yellowstone for fishing.  It is extremely fast .. class 4 and 5 rapids.   I've never been to the lower river but suggest forgetting about the upper.  There is ton of water in the park.   Slough Creek is one of Yellowstone's best.  It's more North Central than Northwest.    If you stay in the Northwest part, the ride to get to the Slough is beautiful but..  the ups and downs and back and forth on that road is annoying.  If you are set in staying in the northwest part, and are into bigger water, try the Madison just outside the northwest corner.

The farther you walk, the less pressure there is (surprise).   In fishing terms.. it's broken up into meadows.  Always keep in the back of your mind (and watch your back) that this is prime grizzly country.   You'd think you'd see them coming in the open meadow but that's not always so.   Don't stand there whaling yer fly pole around like a dumas.   Do lots of crouching and be a sneeky fella .. even if that means staying on the bank in the grasses.
 
Here's a link about the area streams.
 
http://www.flyfishingyellowstonenationalpark.com/streams.html
 

I have fished the Gallatin a little bit in different spots from just outside of Bozeman down to around Big Sky. it does get pressured and it's not really a big trout hot spot (from what i am told) but it seemed to be loaded with fish. Some pretty stuff, too. There are a few good shops in Bozeman that give a nice breakdown on where to go along the way.
 
this was the first placed i fished out west and it took a while to get used to fishing attractor patterns in the pocket water, but once you figure that out there are plenty of fish to catch.
 
haven't fished the strectch in the park, but the stuff i drove by looked like nice meadow/hopper water. smaller fish, i reckon.
 
If you are looking for smaller water with loads of fish, you may want to look at Soda Butte, in the NE corner. the lower you get (closer to the mouth) there are bigger fish. you also have the Lamar right there which is good. But if it were me i would be spending the most time on the Slough. skip the waders and save the room in the back pack for beer (or water, if you are into that kinda thing). it makes the hike in alot easier and you will be hiding in the grass most of the time anyway. Hoppers are the most fun, but streamers get attention, too.

PM sent....

Headed there 7 September....tying hoppers this morning for the trip!