On June 5, 1805, Lewis saw a large creek with some timber in its bottom, but no water, although it had rained all night. It was astonishing, he wrote, "what a quantity of water it takes to saturate the soil of this country. The earth of the plains are now opened in large crivices in many places and yet looks like a rich loam."
For that very reason, throughout most of the 19th century most farmers overleaped the dry land between the 98th meridian--the eastern third of the Dakotas--and the Rocky Mountains. Then, around 1890, with new farming methods and machines at their disposal, and federal legislation to encourage them, they began to break ground even in Marias River country. For a few years it seemed to many that the Jeffersonian dream of a prosperous agrarian lifestyle was finally coming true in the West.
But the wet years--the first fifteen of the century--brought floods that scoured crops from the narrow but fertile river bottoms, and made the gumbo on the highlands hard to till. In the dry years, from 1915 into the twenties, dust storms were more common than rainstorms. In June of 1908, a flood year, the Missouri River raged along at 107,000 cubic feet per second past Fort Benton, 22 miles upstream from the mouth of the Marias. In 1919, at the height of the drought, it trickled by at a pitiful 1,420 cfs.
Major floods occurred in the Missouri River basin in 1844, 1881,1903, 1908, 1915, 1927, and 1948. The Marias River drainage contributed to the problem by adding spring runoff from the northern part of the Rockies. Something had to be done.