Paris Gibson had a vision. The sheep rancher and Minneapolis flour mill operator saw the five waterfalls of the Missouri not as obstacles but as engines waiting to be harnessed. In 1887, with railroad magnate James J. Hill organizing investors from the Great Northern Railway, the Great Falls Water Power & Townsite Company was formed with five million dollars in capital. Gibson promoted his dreamed-of city on the promise of abundant, cheap electricity - but that promise required actually building dams. When the Boston and Montana mining company signed an agreement in September 1889 requiring delivery of power by the following year, the race began. GFWPTC engineers designed a rock-and-timber crib weir dam on the upstream brink of the falls. Workers who built it helped found the adjacent town of Black Eagle; earthen foundations from their shantytown remain visible today.

The 1890 dam represented an earlier age of power transmission. Water turned turbines in two powerhouses flanking the river, but the mechanical energy wasn't primarily converted to electricity. Instead, an elaborate system of ropes and pulleys transferred power directly to the Boston and Montana smelter's equipment. Thomson-Houston generators transformed only some of this mechanical energy into electrical current. By 1892, more than a thousand workers labored at the smelter complex, which grew to include concentrators, furnaces, converters, and an electrolytic refinery. The dam's engineers estimated a fifty-year lifespan for their timber structure - optimistic, perhaps, but not unreasonable given the technology of the era.

In 1926, the Montana Power Company announced a million-dollar reconstruction. The new concrete dam, completed in 1927, rose over the submerged remains of the original timber structure, which was never removed. The rebuilt dam featured an ogee-shaped crest for improved water flow and a powerhouse containing three Allis-Chalmers turbines capable of generating seven megawatts each. The original south forebay was abandoned while the north forebay underwent significant rehabilitation. Workers once walked across the dam's top to reach jobs and schools on the opposite bank - a practice the Montana Power Company ended during World War II for security reasons and never resumed.

Floods have tested Black Eagle Dam repeatedly. In June 1975, more than five inches of rain fell in the Rocky Mountains within 24 hours, forcing the evacuation of 5,000 Great Falls residents when the Sun River rose 18 feet above flood stage. In 1997, rapid snowmelt pushed the Missouri itself 10 feet above flood level. Ice poses different dangers: in December 2010, floating blocks overwhelmed the dam's crest, tearing handrails from the maintenance walkway. The dam's license requires it to release water over the falls between 9 AM and 8 PM on summer weekends and holidays - meaning Black Eagle Falls sometimes runs dry when power generation takes priority. Maintenance drawdowns have repeatedly exposed the Missouri's original channel near Giant Springs.

The island where Lewis spotted that eagle's nest has been transformed. In 2001, Tailrace Island was renamed Black Eagle Memorial Island to honor workers who lost their lives building and operating the dam. The River's Edge Trail, opened in 1991 along former Burlington Northern Railroad tracks, now connects the island to riverside parks and viewing areas. The annual Lewis and Clark Festival in late June and the mid-July Luminaria Walk draw visitors who watch the falls illuminated by colored spotlights. Westslope cutthroat trout, first identified here by Lewis and Clark themselves, still swim these waters. Above the dam, the only two red oak trees in northcentral Montana grow on the hillside - though beavers have proven such persistent threats to local vegetation that officials now protect trees throughout the city's riverside parks.