One of the first dams constructed in Montana was the Black Eagle Dam, a hydroelectric dam constructed of timber and rock, which was built in 1890 on the Missouri River at Great Falls. By 2018 Montana had 3,259 dams that meet the National Dam Inventory (NID) Criteria for storing at least 50-acre feet of water or are at least 25 feet high. These dams are categorized into three categories: large, medium, and small. Large dams can be several hundred feet tall and are often constructed with concrete. Medium dams are typically between 30 and 150 feet tall and of earthen construction. Small dams are generally less than 30 feet tall and sometimes referred to as pond dams; many Montana dams fall into this category. Most Montana dams are held privately, some are federally owned, while others are either maintained by the state, reservation, locally, or by public utilities.

Several of Montana’s early irrigation or reclamation projects were initiated either under the Carey Land Act of 1894, or the Newlands Reclamation Act of 1902, which created the U.S. Reclamation Service (later becoming the U.S. Bureau of Reclamation). Irrigation projects that were completed under the Carey Land Act can briefly be described as a three-cornered partnership between the United States government, the State of Montana, and a private construction company. The government provides the land (public domain) to the state which employed the construction company to build the irrigation works.

In 1895, under the Arid Land Grant Commission, Montana attempted to setup five irrigation districts: District 1, the Billings Bench irrigation canal near Billings; District 2, the Big Timber Creek canal near Big Timber; District 3, a canal about eight miles from Bridger on Rock Creek in Carbon County; District 4, on the Dearborn River near Augusta known as the Dearborn Canal; and District 5, on the Sun River. Districts 1, 3, and 5 were abandoned due to lack of funds. District 2 faced repeated delays and was also not completed. By 1903 only 19 of the projected 55 miles of Dearborn ditch in District 4 were completed and no farmers settled the land.

After investigation by the 1903 Legislature, the Arid Land Grant Commission was abolished and replaced with the Cary Land Act Board. Initially the board was restricted to completing three projects begun in District 1, District 2, and District 4. The 1905 Legislative Assembly expanded their objectives which allowed it to undertake new projects including the Bynum Project, the Conrad-Valier Project, the Teton Project, and several other smaller projects. The Carey Land Act Board existed until 1965 when its duties transferred to the State Water Conservation Board (now known as the State Water Projects Bureau).

The first irrigation district law for Montana was passed in 1907 and delegated the creation of the district and supervision of bond issues to respective boards of county commissioners. The law was amended in 1909 and put power to create districts and authority to control bond issues in the hands of the district court. The Montana Irrigation Commission was created in 1919 by the state legislature. Montana irrigation districts experienced different levels of success, some meeting their financial obligations, while others defaulted on interest and bond payments. Failure on the part of a district wasn’t necessarily a financing or administrative issue; other factors included poor quality land, shortage of water, and expensive construction.

Unlike Carey Act projects, the U.S. Reclamation Service projects remained federal property, even when water users repaid federal construction costs. Reclamation generally contracted with the private sector for construction work, but the projects were administered by Reclamation Service employees to assure that the work met government specifications. Additionally, and particularly so early on, Reclamation Service workers would complete the construction work on a project in the absence of acceptable bids.

Dams, powerplants, and canals constructed by the Reclamation Service helped to pave the way for the expansion of agricultural development in Montana. Some of its earliest projects were in Montana; for example, the Lower Yellowstone Project began in 1905, just three years after the agency was created.

Bonner Dam: a 200-foot long and 30 to 35-foot-tall timber-crib structure, sometimes called the Stimson Dam, was formerly located near Bonner, Montana. The dam was built with 10 x 10-foot timber-crib and filled with rocks by the Montana Improvement Company, and overseen by Walter Coombes, on the Blackfoot River built in 1884 used to hold logs. After floods in 1885 damaged the structure, the dam was rebuilt in 1886 and was reconstructed in 1948 after additional damage was caused by the Blackfoot River. Its steam-powered generator and water powered turbine provided energy to power the mill lights. In 1898 a powerhouse was built that provided 3,400 volts of electricity to Missoula until 1908 when the Milltown Dam (aka Clark’s Dam) was completed. The dam was removed in 2007 during a Federal Superfund cleanup of the Milltown Dam site.

Bynum Dam: a 3,700 foot long and 60-foot-high earth filled dam, with the westernmost quarter mile of the dike faced with concrete on the upstream side, was built five miles from Bynum, Montana by Montana Concrete Construction Company owned by Andrew B. Cook for the Teton Cooperative Reservoir Company circa 1910-1912. The dam was raised 15 feet circa 1924-1926 to increase storage from 75,000 to 90,000-acre feet.

Chessman Dam: a wooden dam composed of heavy timber across the canyon (logs interlaced and filled with rocks and earth) with a base made of earth and stone. The dam was 82 feet broad at its base, 28 feet across the top, and depth of about 25 feet. The dam was constructed about four miles above Rimini, circa 1865-1869 by William A. Chessman during construction of the Chessman reservoir. The reservoir was built for irrigation and to furnish water for Helena. Settling and a large volume of water contributed to a slight crack in the dam. The loads of earth used to patch the leak were insufficient to stop the dam from breaking on August 8, 1876. In 1907 a concrete dam was constructed and created a new reservoir at the head of Beaver Creek.

Fort Peck Dam: the largest hydraulically filled earthen dam in the United States, its reservoir is the country’s fifth largest man-made lake. The dam is nearly four miles in length, 250 feet high, and contains 130 million cubic yards of earth, gravel, and rock. It is located within the Charles M. Russell National Wild Refuge and 20 miles south of Glasgow, Montana. The dam was a major project of the Public Works Administration as part of the New Deal, with construction beginning in 1933 and concluding in 1940. Two powerhouses provide hydroelectric power generation; powerhouse number one contains three units and was completed in 1951, while powerhouse two holds two units and was completed in 1961.

Gibson Dam: a concrete dam 199 feet high and 960 feet long that is an arch gravity structure with a base of 155 feet tapering to 15 feet at its crest. The dam’s construction began in 1926 and was completed by 1929 as part of the Sun River Project. Located on the Sun River, it lies about 60 miles west of Great Falls and 23 miles northwest of Augusta, Montana. It was one of the first dams constructed using the trial-load method. In 1938 gates were installed in the spillway to increase the reservoir’s storage capacity by 20 percent. Legislation was passed in 2023 that authorized hydroelectric development.

Hauser Dam: originally a steel dam built on masonry footings on top of gravel with the ends of the dam anchored in bedrock on either side of the Missouri River about 15 miles northeast of Helena, Montana. The first dam’s construction began in 1905 and was completed by 1907, being built by the Missouri River Power Company and its successor, the United Missouri River Power Company. On April 14, 1908, the dam failed after water pressure undermined the footings. Reconstruction on the dam was completed with concrete by Missouri River Power from July 1908 to 1911. It was rebuilt as a hydroelectric straight gravity dam.

Holter Dam: a hydroelectric straight gravity dam on the Missouri River 45 miles northeast of Helena, Montana. Built between 1908 and 1918, it is 1,364 feet long and 124 feet high. The dam was built by the United Missouri River Power Company and the Montana Power Company. It is a “run-of-the-river-dam” because it can generate electricity without needing to store additional water behind the dam. The reservoir, known as Holter Lake, is 25 miles long with a storage capacity of 243,000 acre-feet of water when full.

Hungry Horse Dam: a concrete arch dam on the South Fork Flathead River located in Flathead National Forest in Flathead County about 15 miles south of the west entrance to Glacier National Park and 20 miles northeast of Kalispell. Construction was authorized in 1944, with the Bureau of Reclamation awarding the construction contract to Morrison-Knudsen and Shea Company, while the Guy F. Atkinson Company won the contract to divert the river during construction. Building began in 1948 and was completed in 1953. Its height is 564 feet, length is 2115 feet, with a base of 320 feet, and crest of 34 feet. The dam’s primary purpose is hydroelectric power generation and flood control.

Libby Dam: a concrete gravity dam on the Kootenai River in northwestern Montana 17 miles upstream from Libby. A joint project between the United States and Canada, construction began in 1966 and was completed in 1972. To make way for the dam the town of Rexford was relocated, and a new Flathead Railroad Tunnel was dug. The dam’s height is 422 feet and length is 3,055 feet. It was constructed to provide flood protection for the Kootenai and lower Columbia Rivers as well as providing an additional source of hydroelectric power for the region.

Madison County/River Dam: a timber-crib hydroelectric dam on the Madison River about 10 miles north of Ennis, Montana. The current structure, constructed between 1905-1906 replaced an earlier dam and powerhouse that went into operation in 1901. As a “run-of-the-river” project, the dam is used for irrigation and generates electricity using the water that flows down the river without needing to store additional water. Its height is 39 feet and length is 257 feet at the crest.

Milltown Dam: a timber-crib, rock-filled gravity-type hydroelectric dam on the Clark Fork River about seven miles east of Missoula, Montana. Built by copper mining tycoon William A. Clark to supply hydroelectric power to nearby Bonner. Construction began in 1905 and was completed in 1908. Its height was 40 feet and length was 219 feet; the sluice gate section of about 52 feet was initially timber-crib but was later replaced with concrete. A matter of months after completion, flooding of the Clark Fork River washed toxic mining sediment downstream from the Anaconda and Butte mines to settle at the base of the dam where it remained until remediation. Milltown Dam was included in the Clark Fork River Superfund Complex in 1992, and after 20 years of remediation and litigation, the removal of the dam took place from 2006-2009. River channel construction and restoration was completed in 2011.

Noxon Dam: an earth-fill gravity-type hydroelectric dam on the Clark Fork River located about 12 miles northwest of Trout Creek, Montana in the far northwest of Montana near the Idaho border. Construction began in 1955 and was completed in 1959. Its height is 260 feet and length is 5,840 feet with a base of 700 feet.

Ryan Dam: also known as the Great Falls Dam, it is a hydroelectric dam on the Missouri River, 10 miles downstream of Great Falls, Montana. Construction began in 1913 and was completed in 1915. The dam was constructed by the Montana Power Company with a height of 61 feet and length of 1,336 feet.

Swift Dam: the original structure was 160 feet high and 465 feet long and was an earth-fill dam with concrete decking, arching upstream, and reinforced with steel rods. The original construction began in 1912 and was finished in 1914 along Birch Creek about 12 miles west of Dupuyer, Montana. The original dam failed on June 8, 1964, due to the spring floods. Reconstruction on the dam began in 1965 and was completed in 1967. The current structure is a concrete-arch structure 205 feet tall and 573 feet long with a 210 feet long emergency spillway.

Vandalia Dam: a reinforced concrete slab and buttress weir-type structure with movable crest gates and auxiliary overflow crest on the Milk River, three miles west of Vandalia, Montana. Construction began in 1913 and was completed in 1917. The dam was constructed with a height of 32 feet and length of 2,350 feet.

Big Horn Canal, Big Horn County: begun in 1892, the project is also known as the Bighorn Ditch Headgate and was completed in 1904. It was designed by William H. Graves and constructed by Crow workers. The canal/ditch irrigated 35,000 acres and was approximately 40 feet wide and 15 feet deep. The Bighorn ditch/canal and its headgate stemmed from an agreement between the Office of Indian Affairs and the Crow Tribe and was ratified by Congress on March 3, 1891.

Big Timber Creek Canal: an irrigation project of the Carey Land Act in the Big Timber district in Sweet Grass County. In 1908 two natural lakes, located in the central portion of Sweet Grass County, were turned into two large reservoirs by Alex and William Glass. Earthen dikes and irrigation canals that extended more than 35 miles were also built and this system was expected to irrigate 17,000 acres of land. In 1895 work began in Big Timber on an irrigation canal by Andrew Wormser of Holland Irrigation Canal Company, but it was not completed until 1911 by the Glass-Lindsay Land Company. The canal was 24 miles in length with an average width of 16 feet at the top, nine feet at the bottom, and was five feet deep and was envisioned to provide irrigation for 100,000 acres of land. The project reclaimed 50,000 acres in the Big Timber district.

Flathead Irrigation Project: an irrigation project located south of Flathead Lake in Lake County. Construction was started in 1907 with plans to provide for the irrigation of about 152,000 acres of land and was completed in 1963. The project is separated into three geographical divisions that include the Camas Division, the Mission Valley Division, and the Jocko Division. In 1960 the irrigation system consisted of 15 reservoirs with a total capacity of 148,728 feet; 1300 feet of collection, carriage, distribution canals, and laterals; 150 major irrigation structures; and 10,000 minor structures.

Irrigation Projects – Miscellaneous:

￮ Billings Bench Irrigation Canal: also referred to as the Billings Bench Water Association Canal. A canal on the Yellowstone River; it started in Laurel, ran through Billings, and ended near Shepherd, Montana. The project started in 1903 and in 1905 an 1,847-foot tunnel, a 900-foot flume, and nearly 100 miles of canals and laterals were completed. It was the first Carey Land Act project in Montana to be completed successfully and was projected to provide water to over 18,000 acres of land.

￮ Hardin Irrigation Project: an irrigation project of the Big Horn Low Line Canal Company located 5 miles north of Hardin and extended north along the Big Horn River for about 10 miles. Water was taken by gravity from the Big Horn River, covering a gross area of 10,000 acres, with about 7,500 acres irrigated in 1932.

￮ Huntley Irrigation Project: one of the first irrigation projects of the U.S. Reclamation Service. Project works included a rock-fill and concrete diversion dam, 32 miles of main canal, 22 miles of carriage canals, 202 miles of laterals, 186.5 miles of drains, a hydraulic turbine-drive pumping plant, and an auxiliary electric pumping plant. The project was in south-central Montana and established from land that was ceded from the Crow Indian Reservation. Construction began on the project in 1905 and was completed in 1937; it furnished water to approximately 30,000 acres. Water supply and water distribution works included a main canal and distribution system on the Yellowstone River near Huntley; a pumping plant near Ballantine; Anita Dam and reservoir; and Yellowstone Diversion Dam southwest of Huntley. The Yellowstone River Diversion Dam was rehabilitated in 1957 after a crack was found in the dam due to settlement.

￮ Joplin well drilling: insufficient information available for the project.

￮ Lower Yellowstone Irrigation Project: one of the first irrigation projects of the U.S. Reclamation Service. Construction of the system started in 1905 and was completed by 1912 with the main canal at 72 miles long and 225 miles of lateral canals. A 100-mile drainage system was completed by 1931.

￮ Northern Pacific irrigation headgate: insufficient information available for the project.

Milk River Irrigation project: an irrigation project in north-central Montana containing 121,000 acres of irrigated land, lying mostly in a narrow strip on both sides of the main line of the Great Northern Railway in Blaine, Phillips, and Valley counties. In the early 1900’s the U.S. Reclamation Service began construction of several pieces of the project on the Blackfeet Indian Reservation near Glacier National Park: a storage facility (Lake Sherburne on Swiftcurrent Creek), the St. Mary Diversion Dam, and the St. Mary Canal. Together, these works carried water from the St. Mary River to the North Fork of the Milk River. Facilities along the Milk River in north central Montana, the eastern part of the project, were built later: Nelson Reservoir was added in 1922 and in the 1930’s the Fresno Reservoir was constructed. Other water supply and distribution works built included the Paradise Diversion Dam, Dodson Diversion Dam, Vandalia Diversion Dam, and Dodson Pumping Plant. As of 1986 the Milk River Basin contained over 138,000 irrigated acres that include 92,000 acres located within the Milk River Project. 2023 statistics state the project furnishes water for irrigation to 121,000 acres of land via 200 miles of canals, 219 miles of laterals, and 295 miles of drains.

Sun River Reclamation project: an irrigation project located in Teton and Cascade counties about 30 to 40 miles north and west of Great Falls comprising an area of 6 by 17 miles. Divided into two major parts, the Fort Shaw division consists of about 13,900 acres in operation starting in 1908 and the Greenfields division comprising Greenfields Bench, Big Coulee, and Sun River Slope that was investigated in 1903, but not recommended for construction of 25,000 acres until 1910. By 1923 the total Greenfields acreage was expanded to 46,000, with an additional 9,000 acres added in 1936. Planned water storage for the project included Willow Creek Dam and reservoir on Willow Creek; the Gibson Dam and reservoir on Sun River; the diversion of water from the North Fork of Sun River into Pishkun Supply Canal, Pishkun Dikes and reservoir, and the diversion of water from the Sun River into the canal system which irrigates the Fort Shaw division. Other water supply and water distribution works include the Sun River Diversion Dam, Willow Creek Feeder Canal, Fort Shaw Canal, and Sun River Slope Canal System.

Valier [Conrad-Valier] Irrigation project: an irrigation project of the Carey Land Act in Pondera County. The project was slated to turn 150,000 acres of range land into irrigated farms. The water comes from Birch and Dupuyer creeks, which were tapped by a large canal and water was impounded in reservoirs that include Lake Frances and Birch Creek reservoir.