page_title: History of Saint Paul, Minnesota
section_title: Geological history
hierarchical_section_title: History of Saint Paul, Minnesota / Geological history
caption_attribution_description: English: Canoes at Phalen Lake, St. Paul, Minnesota, 1905.
context_page_description: Saint Paul is the second largest city in the state of Minnesota in the United States, the county seat of Ramsey County, and the state capital of Minnesota. The origin and growth of the city was spurred by the proximity of Fort Snelling, the first major United States military presence in the area, and by its location on the Upper Mississippi River, with the northernmost natural navigable port on the mighty river.
  Fort Snelling, originally known as Fort Saint Anthony, was established in 1819, at the confluence of the Mississippi and Minnesota rivers in order to establish American dominance of the fur-trading industry on the rivers. As the whiskey trade started to flourish, the military officers in Fort Snelling banned the distillers from the land the fort controlled, with one retired French Canadian fur trader turned bootlegger, Pierre "Pig's Eye" Parrant particularly irritating the officials. In 1838, Parrant moved his abode and operation downstream about 5 miles to the north bank of the river in what is now downtown Saint Paul. There Parrant established the area which became known as "L'Oeil de Cochon" and the new location began to be settled by French Canadians.
context_section_description: During Upper Cambrian and Ordovician time, from approximately 505 to 438 million years ago, shallow tropical seas covered much of then-equatorial southeastern Minnesota. During this time, the sedimentary rocks that constitute the bedrock of St. Paul were deposited. The most visible of these are the 156-foot (48 m) to 166-foot (51 m) thick layer of St. Peter Sandstone, the lowest layer of sedimentary rock above the Mississippi River in Saint Paul, which is overlain by a thin—3-foot (1 m) to 5.5-foot (2 m) thick—layer of Glenwood Shale, and capped by a 28-foot (9 m) thick layer of Platteville Limestone. These units are overlain by the fossiliferous Decorah Shale, which is in some places completely eroded and in others up to 95 feet (29 m) thick, and exposed at the brickyards, a popular fossil hunting location in Lilydale Park. All of the units exposed on the surface in St. Paul are of Ordovician age. Marine fossils can be seen embedded in limestone structures, such as the Henry Hastings Sibley House.
  About 20,000 years ago, the area was covered by the Superior Lobe of the Laurentide Ice Sheet, which left the St. Croix moraine on the Twin Cities as it receded.  Later the Grantsburg Sublobe of the Des Moines Lobe also covered the area. These thick layers of ice cut through the Platteville limestone cap rock with tremendous force, forming tunnel valleys, and released glacial meltwater. The result was a series of troughs in the limestone, which were filled by glacial till and outwash deposit as the glaciers receded.  Sometimes the sediment would be mixed with huge chunks of ice, which would leave voids, or kettles, in the soil. These kettles later filled with water and became Lake Como and Lake Phalen.
  Glacial River Warren was a prehistoric river that drained Lake Agassiz in central North America between 11,700 and 9,400 years ago. Lake Agassiz, which was up to 600–700 feet (~200 m) deep, and at various times covered areas totaling over 110,000 square miles (~300,000 km²), was formed from the meltwaters of the Laurentide Ice Sheet during the Wisconsonian glaciation of the last ice age. The enormous outflow from this lake carved a wide valley now occupied by the much smaller Minnesota River and the Upper Mississippi River below its confluence with the Minnesota. Blocked by an ice sheet to the north, the lake water rose until about 9,700 years Before Present (BP), when it overtopped the Big Stone Moraine, a ridge of glacial drift left by the receding glacier, at the location of Browns Valley, Minnesota. The lake's outflow was catastrophic at times, creating a wide valley to Saint Paul, where the massive River Warren Falls once graced the landscape. Over 1700 years this waterfall retreated upstream and undercut the Mississippi at the site of Fort Snelling. The falls then split.  The Mississippi falls migrated upstream to form Saint Anthony Falls and create Minnehaha Falls in Minneapolis.  The River Warren falls receded west in the Minnesota River valley until they reached an older buried river valley about two miles (3 km) west of the confluence, where the falls were extinguished. The high bluffs on either side of the river represent the channel dug by the River Warren as it carried massive volumes of water through Saint Paul.
caption: Lake Phalen in 1905
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