Minnehaha Creek is a tributary of the Mississippi River located in Hennepin County, Minnesota that extends from Lake Minnetonka in the west and flows east for 22 miles (35 km) through several suburbs west of Minneapolis and then through south Minneapolis. Including Lake Minnetonka, the watershed for the creek covers 181 square miles (470 km2). The creek might have been unremarkable except for the 53-foot (16 m) Minnehaha Falls located near the creek's confluence with the Mississippi. The site is not far from Fort Snelling, one of the earliest white settlements in the region.
Visitors to the park can view the ancient geological history of Minnesota as they walk the path leading from the upper falls down to the Mississippi River. The uppermost layer of soils and gravels of Minnesota were deposited by the most recent Ice Age, about 10,000 years ago. Four great ice ages have swept away all traces of the more recent Mesozoic and Cenozoic eras in the Twin Cities area, however standing at the upper falls, one is standing directly on the Platteville Limestone Formation laid down during the Ordovician Period of the Paleozoic Era.
During the Ordovician Period, about 450 million years ago, the North American continent was situated along the equator, and a warm shallow sea covered much of Minnesota. Sea life was abundant and a large number of marine fossils including corals, bryozoans, brachiopods, clams, snails, cephalopods, and trilobites can be found in the limestone and shale sediments at several areas in the Twin Cities and along the Mississippi River in the park and elsewhere.