On May 31, 1805, Lewis and Clark proceeded their journey through the Missouri Breaks. Lewis wrote: “The bluffs of the river rise to the height of from 2 to 300 feet and in most places nearly perpendicular; they are formed of remarkable white sandstone which is sufficiently soft to give way readily to the impression of water; two or three thin horizontal strata of white free-stone, on which the rains or water make no impression, lie embedded in these cliffs of soft stone near the upper part of them; the earth on the top of these cliffs is a dark rich loam, which forms a gradually ascending plain that extends back from 1⁄2 a mile to a mile where the hills commence and rise abruptly to a height of about 300 feet more. The water in the course of time in descending from those hills and plains on either side of the river has trickled down the soft sand cliffs and worn it into a thousand grotesque figures.”