The Giant Springs Heritage State Park is a 218-acre facility which includes the spring, hatchery, and the regional headquarters and visitor center for the Montana Department of Fish, Wildlife, and Parks. The spring is an unforgettable experience. About 7.9 million gallons of water run through the spring each hour making it the largest freshwater spring in the United States. Lewis and Clark were astonished at its size and Lewis wrote that it was the “largest fountain I ever saw…”
Not only does it claim the “largest spring” status, but the Roe River which flows from the Springs to the Missouri is the shortest river in the world at a mere 53 feet long. There is also a fish hatchery here where more than one million Rainbow Trout are raised each year and you’re more than welcome to feed the fish. Keep your eyes open here for raccoons, beaver, pelicans, bald eagles, deer and more.
Madison Limestone lied under most of eastern Montana and is about 250 million years old. Rainfall and melted snow soak into the limestone where it is exposed on the slopes of the Little Belt Mountains. The water drains downward and then flows through openings in the limestone to the Great Falls area where it flows upward about 700 feet through fractures. It is then forced out at Giant Springs by a force of about 300 pounds per square inch. Giant Springs discharges about 134 thousand gallons per minute. It contains calcium, magnesium, bicarbonate, and sulfate. It is excellent for growing Trout. The entire trip of 38 miles from the Little Belts to Giant Springs takes many hundreds of years.
Text of interpretive sign at site.