From Lewistown drive 4.5 miles south on MT 238 to MT 466. Go right and drive two miles. Located in the Snowy Mountains, Big Spring is the third largest freshwater spring in the world and is the source of Spring Creek. Over 90 million gallons of water a day flow out of the Spring. Also here is the Montana State Fish Hatchery. It is one of the three largest fish hatcheries in the west. More than 3 million trout are raised here each year. From the hatchery, go back to Hwy.. 238 and head south for about 12 miles to the East Fork Recreation Area. There is fishing and a boat launch site here, plus picnic tables and grills, restrooms, and a campground.