On August 21, 1804, Lewis and Clark passed the mouth of the Big Sioux River during their journey, recording that they set out very early, traveled under a gentle breeze from the southeast, passed Willow Creek below a bluff about 170 feet high and above Floyd's River, and then passed the Sioux River on the starboard side. They wrote that, according to Mr. Durrien, their Sioux interpreter, the river was about the size of the Grand River and navigable to falls 70 to 80 leagues upstream, where falls about 200 feet high had two principal pitches, and that below the falls a creek ran through red rock cliffs from which Indians made pipes and where different nations met in peace at the quarries. The expedition passed through this area again on their return on September 4, 1806. In 1804, the Missouri River passed the mouth of the Big Sioux and swung north toward the McCook Lake area before proceeding west.