Geography of Chicago

The city of Chicago is located in northern Illinois, United States, at the south western tip of Lake Michigan.

It sits on the Saint Lawrence Seaway continental divide at the site of the Chicago Portage, an ancient trade route connecting the Mississippi River and the Great Lakes watersheds.

One special feature of the Chicago area was the now-vanished Mud Lake in the Des Plaines River watershed.

During heavy periods of rain or when the Des Plaines overflowed its banks due to downstream ice dams in the early spring, the river would flow through Mud Lake to the South Branch of the Chicago River, forming a favorite portage for early traders and creating the path of the future I&M and Chicago Sanitary and Ship Canals.

When the city we know today was initially founded in the 1830s, the land was swampy and most of the early building began on low dunes around the Chicago River's mouth.

Indeed, Chicago's low lying geography, which ultimately became crucial to its boom town development (as the site of the Chicago Portage and canal), could not initially attract substantial early settlement because the tall grass prairie around its lake and river systems was underlain by hard packed glacial clay, making much of the area forbidding wetlands.

[2] Thus, the paradox of Chicago's development as a city in the 19th century became taking advantage of this geography, but also overcoming its limitations.

[3] The Silurian dolostone bedrock is also exposed at the ground surface when the Kennedy Expressway dips below the UP Northwest Line near Addison Street.

According to the National Weather Service, Chicago's highest official temperature reading of 107 °F (42 °C) was recorded on June 1, 1934.

Summer is typically the rainiest season, with short-lived rainfall and thunderstorms more common than prolonged rainy periods.

[6] According to the United States Census Bureau, the City of Chicago has a total area of 606.1 km2 (234.0 sq mi).

The centroid (geographical center) of the city is at 41°50′26″N 87°40′46″W / 41.840675°N 87.679365°W / 41.840675; -87.679365,[16] southeast of 28th and Leavitt Streets in an industrial area near the Chicago Sanitary and Ship Canal.

By modern standards, Chicago has little reason to build up: being located in the Midwest, it has plenty of room to sprawl outwards on almost Euclideanesque flat ground.