Cottonwood trees played a vital role in the success of the Lewis and Clark Expedition. On November 9, 1804, William Clark wrote, "We are situated in a point of the Missouri North side in a Cotton wood Timbery this Timber is tall and heavy." Like many American Indians, these early explorers depended on cottonwood for building materials, tools, and fuel. The cottonwood forest lining the banks of the Missouri River provided a protected place to build and to hunt for food. Members of the Corps of Discovery used cottonwood to construct Fort Mandan and learned from their Mandan and Hidatsa neighbors that cottonwood bark, twigs, and young branches and saplings made good feed for their horses. Cottonwood released its cottony seed each year to coincide with spring floodwaters. Its seedlings require bare moist soil, and the exposed sandbars of the Missouri River provided prime locations for growth. The construction of dams has inundated much of the cottonwood forests in North Dakota and eliminated the natural flooding, which has significantly reduced the available habitat for young cottonwoods.