Big Arm State Park 
28031 Big Arm State Park Rd.
Big Arm, MT 59910
406-752-5501
http://stateparks.mt.gov/big-arm/
State Park: Bike, Birding, Camp, Fish, Hike, Horse, Picnic, Walk, Water Sports
Camping, a long beach, nature trail, and a yurt rental are all here. This park is a popular jump-off point to Wild Horse Island, using the ramp to launch your own boat.