St. Louis was still under Spanish control at the time Thomas Jefferson dispatched Lewis & Clark and the 'Corps of Discovery' on their mission. Captain Lewis spent most of the winter of 1803 -1804 in St. Louis making preparations for the journey and awaiting official transfer of the territory from Spanish to French and then to United States control.

During that time, the rest of the party camped upriver from St. Louis in Wood River, Illinois. Camp Dubois, as it was called, was on the Mississippi's eastern shore but the exact site is now thought to be in Missouri because over the centuries flood and erosion have shifted the river's course.