Giant Springs

Useful Information

Location: 4803 Giant Springs Rd. Great Falls, MT 59405.
Giant Springs State Park
(47.534314, -111.230138)
Open: All year daily sunrise-sunset.
Fee: Car USD 8, By Foot USD 4, Bicycle USD 4, Bus Passenger USD 4.
Classification: KarstKarst Spring
Light: n/a
Dimension: Yavg=6,835 l/s, T=12 °C.
Guided tours: self guided,
V=300,000/a [2019]
Photography: allowed
Accessibility: no
Address: Giant Springs State Park, 4803 Giant Springs Rd. Great Falls, MT 59405, Tel: +1-406-727-1212. E-mail:
As far as we know this information was accurate when it was published (see years in brackets), but may have changed since then.
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18-JUN-1805 discovered by the Lewis and Clark expedition.
1883 City of Great Falls founded nearby.
1970s Giant Springs State Park established.


Giant Springs is one of the largest freshwater springs in the U.S.A., classified as magnitude 1 spring. It is fed by the Madison aquifer, a vast aquifer underlying five U.S. States and three Canadian Provinces. It flows through the karstified Madison Limestone, so it is actually a karst spring. However, this is not the outflow of the aquifer, only one of them. The catchment area are the Little Belt Mountains. The aquifer eventually surfaces in Canada and water from the Black Hills, Big Horn Mountains and other areas join the aquifer before it resurfaces.

Quite exceptional for a karst spring is the fact that the water takes approximately 26 years to reach the springs, which is extremely long for karst and a result of the enormous size of the aquifer. There were even researches dating the water to be about 3,000 years underground. This has numerous effects which are quite unlikely and untypical for karst springs. It is not only perennial but has a constant flow. The water temperature is constant at 12 °C, even in the coldest winter. The water is very pure as it was cleaned chemically by the limestone and biologically by microorganisms, which normally does not work very well in karst because karst water is often underground for only a few days.

But it has also properties which are typical for a karst spring. The production is very high which is a result that the karstified limestone has caves which are wide channels for the water. Magnitude 1 springs are actually almost always karst springs. The water has a high content of limestone, which is called "hard" water. The limestone content is responsible for the blue colour of the spring, when the sun shines on the water. This is caused by the dissolved limestone which filters the white sunlight but the blue wavelengths less than the others.

The spring has other, not geological superlative to offer. It is the most visited State Park in Montana, with over 300,000 visits per year. And it produces the shortest river, as it is located right on the shores of the Missouri River. It's hard to measure, but probably it's 61 m long. We are not so sure about this, because the spring is located only 6 m from the Missouri, and half the water flows directly into the river. But the other half flows almost parallel to the river and then joins the Missouri. This runoff has a name, it is called the Roe River, and creates the Roe Island. Roe River was listed in the Guinness Book of World Records as the world’s shortest river. It's not listed any more as they removed this category.

“the largest fountain or Spring I ever Saw, and doubt if it is not the largest in America Known, this water boils up from under th rocks near the edge of the river and falls imediately into the river 8 feet and keeps its Colour for ½ a mile which is emencely Clear and of a bluish Cast.”
Diary of William Clark on June 18, 1805.

The spring was used by the Blackfeet people as an easy-to-access water source in the winter. The spring was discovered by the Lewis & Clark Expedition in 1805 during their exploration of the Louisiana Purchase. Settlers ignored the spring until 1884 when the town of Great Falls was established and the springs became the place for Sunday recreational activities.

Giant Springs State Park was established in the 1970s and is much bigger than just the area of the springs. It includes four waterfalls of the Missouri River and five hydroelectric dams owned by Northwestern Energy. There is the opportunity for river fishing and hunting waterfowl, upland game birds, and deer. The park is the only State Park with a fish hatchery located within its boundaries, called Giant Springs State Fish Hatchery. It is also the starting point of numerous walks. Nearby are interesting museums like the Montana Fish, Wildlife & Parks Visitor Center and the Lewis and Clark Interpretive Center.