In May 1804 Meriwether Lewis, William Clark, and the Corps of Discovery embarked on a seven-thousand-mile journey with instructions from President Thomas Jefferson to ascend the Missouri River to its source and continue on to the Pacific. They had spent five months in the St. Louis area preparing for the expedition that began with a six-hundred-mile, ten-week crossing of the future state of Missouri. Prior to this, the explorers had already seen about...