The previous Lewis & Clark Bridge at this location was a big metal monster of a through truss bridge with four truss spans. That bridge was built in 1927, and removed in 1973 when it became obsolete compared to modern traffic demands and ever heavier trucks. Two piers from that bridge still exist and are visible in the upper photo. I also found records of an earlier pontoon bridge that was built in 1916, but was destroyed in a flood in 1918. I am not sure if that was the first bridge at this location, or if there were any bridges between 1918 and 1927.
The river at Williston is a river in transition. Up river, the Missouri more or less runs free after passing the Fort Peck Dam. Currents can reach as high as seven miles per hour as the river drops 188 feet. Below Williston, the river is part of the gigantic Lake Sakakawea. The river drops less than four feet over the next 160 miles, with the current dropping to less than two miles per hour. The result is that the suddenly slowing water tends to drop much of its sediment in the Williston area. This results in a lot of sandbars and frequently shifting channels. This impacted the City of Williston by seriously degrading its quality of drinking water when its city water intake ended up in an area of stagnant water cut off from the river by a sandbar. The city solved the problem by building a new water intake in the middle of the river channel next to the highway bridge. That water intake can be seen in the photo above. It is the concrete structure that is connected to the bridge by a short steel walkway.