A Company Town on the Missouri Bluff
Riverdale does not look like other McLean County towns. There is no grain elevator anchoring the skyline, no main street that grew up around a railroad depot, no century-old storefront with peeling paint and a pressed-tin ceiling. Riverdale was designed from scratch, in the late 1940s and early 1950s, to house the workforce building the Garrison Dam — and the blueprint is still visible in every wide, planned street and modest ranch-style house. It is a government town, built by the U.S. Army Corps of Engineers, and it has that quality you find in government towns: orderly, functional, slightly outside of time.
The site made sense. Perched on the bluffs above the Missouri River just downstream of where the dam would rise, it had commanding views and easy access to the construction site. Workers arrived from across the country — engineers, heavy-equipment operators, laborers — and Riverdale grew quickly into a small, self-contained community with housing, a school, a post office, and the infrastructure a major federal project demands. At its peak, the population reached several thousand. The dam was the reason for everything.
Garrison Dam itself is the largest rolled-earth dam in the United States by volume, and its construction through the early 1950s was one of the largest civil engineering projects in the postwar West. Riverdale was where the people who built it ate breakfast and put their kids to bed. That history is not always loudly announced here, but it is in the bones of every street.
What Stayed and What Changed
When the dam was completed and the Army Corps of Engineers wound down its construction operation, Riverdale faced the question every company town eventually faces: what are you without the company? Some workers left. Some stayed. The town incorporated and carried on, though at a fraction of its construction-era size. Today it is a small, quiet community — the kind of place that appears briefly on a highway map and might not detain a traveler long, but rewards a short stop.
The physical plant of the original government construction camp has been substantially altered over the decades, though the planned-community layout is unmistakable to anyone paying attention. Streets are wider than you would expect for a town this size. Lots are regular and generous. The whole place has an uncluttered, mid-century feel that has less to do with preservation than with the simple fact that not much was added after the original build.
What draws people to this part of the county now is mostly the reservoir itself. Lake Sakakawea stretches for miles upstream from the dam, and Riverdale sits at the eastern end of that engineering story — the controlled, downstream end where the dam's massive earthen face holds back one of the largest man-made reservoirs in the United States. Driving out toward the dam structure from Riverdale, you get a scale that photographs never quite capture: the earthen face rising wide and gradual above the river valley, the powerhouse at its base, the Missouri running cold and clear below it, altogether different from the warm, silted river that once moved here freely.
The Dam Road and the Downstream River
The road that runs out to and across the top of Garrison Dam is one of the more unusual drives in the county. From it you look south into the downstream river valley — a reach of the Missouri that runs cold and relatively narrow below the dam, its character shaped entirely by what the Army Corps of Engineers releases from the reservoir above. This is a different river than the one Lewis and Clark poled upriver in the early nineteenth century: steadier in flow, colder in temperature, cleaner in clarity, and in some ways ecologically transformed by that steadiness. The contrast with the wild, braided river of the historical record is worth sitting with.
Riverdale itself is the logical base for anyone who wants to spend time at the dam rather than just photograph it from the highway. The community is small and services are limited, so arrive prepared — but the position on the bluff, with the reservoir glinting to the north and the engineered river running south, is genuinely striking. The town's surrounding landscape is open Missouri Plateau country: big sky, rolling breaks, the kind of scenery that does not perform for you but opens up quietly if you stay in it.
For the traveler moving between Washburn to the east and Garrison to the northwest, Riverdale is the hinge point — the place that explains why both the lake and the downstream river are what they are today. It would be easy to drive through without stopping. It is better to pause, walk to a bluff edge, and look both ways along the valley. The dam is right there. The town behind you exists because of it. That is the whole story, and it is a substantial one.
How it happened
- late 1940s–early 1950sRiverdale built to house Garrison Dam construction workforce
- early 1950sGarrison Dam construction completed