This is a beautiful map - what's it of?

We are just after the confluence of the Missouri and Mississippi Rivers. This is the entry to the Chain of Rocks Canal, which was built in the 1940s to allow easier navigation through a wide and shallow part of the Mississippi River. This part of the river has an exposed bedrock. The Chain of Rocks roughly marks the extend of glaciation in Missouri. Glacial melt shifted the Mississippi River toward the west side of the American Bottom, from previous easterly bends. During the development of the St. Louis region, before the Chain of Rocks Canal, boats had to wait, sometimes days, for the river to reach a safe height for traversing this shallow, rocky part of the Mississippi River.