Smith River State Park and corridor isn't a discrete state park per se, so much as a collection of pearl-like campsites strung along the otherwise private banks of one of Montana's crown fishing-and-floating jewels.
Several characteristics distinguish the Smith River from its peers in a state full of great rivers. For one, there's no public access whatsoever between the put-in at Camp Baker and the take-out at Eden Bridge, 59 miles downstream. For another, the Smith is the only Montana River managed under a permit system by Montana Fish, Wildlife & Parks. To float the Smith, you'll need to apply for and win a permit in the annual FW&P-run lottery. For more information, check out the Smith River Floating page.
Once you're on, the envy of your friends who applied and failed, you're in for a treat. The river's remoteness and FW&P's permitting system mean you'll be able to enjoy a relatively uncrowded river for what's typically a 3- to 4-day trip. Twenty-seven boat camps with 52 campsites give floaters plenty of breathing room, and each camp's primitive toilet is famously located for maximum privacy and expansive views.
The Smith's narrow canyons, sharp turns, and generally quick water are well suited for rafting fishermen and canoeists prepared to pay attention, and both the wildlife-viewing and the fishing are extraordinary. Taking a trout at sunset beneath the glowing wall of Sunset Cliffs may be enough of a quintessentially Montana experience to last you a lifetime.