This sandstone originated as a sheet of sand in clear, shallow water near the shore of a Paleozoic sea and consists of fine-to-medium-size, well-rounded quartz grains with frosted surfaces.

The extent of the formation spans north–south from Minnesota to Arkansas and east–west from Illinois into Nebraska and South Dakota.

In Minnesota, the soft St. Peter Sandstone can be observed at the bluffs of the Mississippi River valley beneath a very thin layer of Glenwood Shale and a much thicker layer of Platteville limestone.

In Illinois, Castle Rock is a large bluff of St. Peter Sandstone, and Starved Rock State Park and Matthiessen State Park feature numerous outcroppings and canyons.

St. Peter sandstone, also called "Ottawa Sand" in commercial applications, has a relatively uniform size and shape for each grain.