The Mississippi River In Forest Park
More than 300,000 years ago the Mississippi did flow through the eastern edge of Forest Park during the Illinoian glacial period.
The Museum of Science and Natural History has placed a plaque to mark the location of the ancient riverbed and explain how the mighty river was dislodged from its customary path by a lobe of glacial ice.
The plaque was located on Clayton Road in Forest Park just east of the entrance to the St. Louis Science Center but it was removed after being vandalized.
An article from "Discovery/Exploring magazine, Fall 1983 by Kenneth G. Brill Jr. discussed the time when the Mississippi River ran through Forest Park:
"During the third great advance of the Ice Age, glaciers (the Illinoian Stage), much of the present state of Illinois was covered by glacial ice. Some of the meltwater from the ice flowed along the western edge of the glacier in a channel that is now the Mississippi River.
"The size of the river is not known; however, just upstream from St. Louis, it was joined by the Missouri River, thus in times of melting it must have been a fairly large stream.
"Glacial ice is far from clean. It contains fragments of rock debris of all sizes - boulders, pebbles, sand and clay. When the ice melts, a distinctive type of sediment accumulates on the ground. It is an unsorted jumble of rock fragments of all sizes which is called till.
"The distribution of till in St. Louis leads us to believe that the glacier advanced no farther west than Kingshighway.
"Due to vagaries in ice motion, glaciers tend to flow in lobate patterns. During the early phase of the advance of the glacier into St. Louis, a lobe of ice seems to have moved from the Illinois side westward across the Mississippi River into northern St. Louis.
"This lobe of ice temporarily dammed the river, causing ponding of the water upstream from the ice lobe.
"The ponded water extended ten to twenty miles up the Mississippi, Missouri and Illinois rivers and may have been responsible for bench-like terraces along these rivers and their tributaries.
"At times the water flooded portions of northern St. Louis County. Eventually, the level of the ponded water rose high enough to overflow at the lowest point on the downstream side. This low point is believed to have been the valley between O'Fallon Park and Bellefontaine Cemetery through which Interstate 70 and the Terminal Railroad pass today.
"From here the waters flowed southward in a broad channel parallel to Kingshighway. This channel is best seen today in the depression on the east side of Forest Park between the Planetarium and the hospitals. This depression is now a segment of the valley of the River des Peres, a stream which is confined to a sewer beneath the valley.
"Two small man-made lakes (Bowl and Jefferson Lakes) mark the bottom of the valley. The glacial meltwater in this channel flowed around the southwest side of the ice lobe and returned to the Mississippi via Mill Creek Valley. In doing this it apparently flowed through the valley that is crossed by the Kingshighway viaduct just south of Manchester Avenue, and continued eastward parallel to the railroad tracks.
"Mill Creek itself rises in a spring near the railroad tracks west of Tower Grove Avenue. In historic times, Mill Creek was ponded where Union Station now stands and furnished water-power for a grist mill. The Creek is now in a sewer that lies beneath the railroad yards. Mill Creek is what is known as a misfit stream, that is to say, its valley is much too large for the size of the stream. (The valley is four-tenths of a mile wide at Grand Boulevard). Apparently the flow of the glacial-age Mississippi greatly enlarged the valley.
"During a late phase of glacial advance in the area, the lobe of ice enlarged and moved into southern St. Louis. This blocked the Mill Creek channel and forced the waters to find a new southward course to reach the Mississippi.
"From the southeast corner of Forest Park the waters turned westward and formed the portion of the present valley of the River des Peres, which parallels Manchester Avenue from Macklind Avenue to Maplewood. There, the stream joined Deer Creek and flowed southward along the City Limits to join the Mississippi Valley at the south side of present St. Louis. The River des Peres is a misfit stream for the same reason that Mill Creek is.
"Eventually, the lobe of ice that blocked the Mississippi River melted and the river returned to its original course between Missouri and Illinois; however, it left a record of its temporary diversion in till deposits and misfit stream channels."