Montana is well known as a fishing paradise, and some of the nation’s best streams are in the southwestern part of the state. Be sure to pick up a fishing license (available at any fly shop) and check the fishing regulations. Don’t be surprised to find that almost everybody here is a catch-and-release fly angler, even in places where that’s not mandated. The state maintains many fishing access areas near bridges and stream banks; any special regulations or precautions are posted at these fishing sites. Most fishing access areas are also de facto campgrounds. Though the following itinerary is broken down day by day, it’s ideal to allow at least two days at each spot to become acquainted with the local stream habitats.
Pack your fly rod and waders and head south from Missoula  along Highway 93 to the Bitterroot Valley , where the many fishing access sites  make it easy to get to the river. Fish the Bitterroot for rainbow, brown, and westslope cutthroat trout as well as some brookies and bull trout.
It’s easy to camp in the Bitterroot National Forest or to find a place to stay in one of the several small towns in the valley.
Hamilton , 50 miles south of Missoula, is the biggest, and a popular base.
Just south of Conner, the river divides into east and west forks. Continue south along Highway 93, which follows the East Fork of the Bitterroot as far as Sula. Stay on 93 as the river bends east, and head to the Continental Divide at Lost Trail Pass, about 50 miles south of Hamilton . Turn west onto Highway 43 and head down into the Big Hole, a beautiful vast high valley.
Plan to spend a night in Jackson , about 50 miles east of the pass, at the Jackson Hot Springs  (it’s your only choice in this small town, but a good one) and fish the Big Hole River . In the Big Hole you’ll find the expected assortment of trout, but also a few arctic grayling.
From Jackson , follow the river’s wide arc along the northern edge of the valley (highways 278 and 43 and I-15 form this 160-mile loop of the Big Hole), through Wisdom , Wise River, Divide, Silver Star, and Melrose , all tiny towns with few amenities. If you’re really taking your time, this trip could take a few days.
On the southeastern rim of the Big Hole and conveniently located on I-15, Dillon makes a good base.
From Dillon, catch Highway 41 along the Beaverhead River and follow it 29 miles to Twin Bridges (home of the R. L. Winston Rod Company), where the Beaverhead and the Big Hole  join to form the Jefferson River.
After exploring these streams, head 43 miles east on Highway 287 past Virginia and Nevada Cities to Ennis , a Madison River town that has staked its claim on fly-fishing.
Fish the Madison  upstream of Ennis, then head 45 miles north on Highway 287 to Three Forks , where the Madison, Jefferson, and Gallatin Rivers meet at the Missouri Headwaters State Park . This is a powerful place to visit and a decent enough place to cast a line.
In Three Forks, longtime fishing guide Bud Lilly has turned an old rooming house into, well, a fixed-up old rooming house  for anglers.
From Three Forks, travel east on I-90 for 24 miles, then turn south at Belgrade (Highway 85, which becomes Highway 191) to fish the Gallatin all the way south to West Yellowstone (some 90 miles), where you find the upper reaches of the Madison River. Enter Yellowstone National Park for the Firehole, the Gibbon, and the Yellowstone.
Follow the Yellowstone downstream, north along Highway 89, into Montana’s Paradise Valley , where a night at Chico Hot Springs  is always a treat, especially if you’ve been camping for a while. It’s about 75 miles from West Yellowstone.
Take a couple days (or as long as you like) to fish the 23-mile stretch of the Yellowstone between Chico and Livingston , which is 26 miles east of Bozeman  on I-90. Though Highway 89 follows the Yellowstone, the East River Road, which parallels 89 on the east side of the river, is a good option. By then it’ll probably be time to dry out those waders and head home.