Lake Michigan in the context of "Chicago"

The Great Lakes, also called the Great Lakes of North America, are a series of large interconnected freshwater lakes spanning the Canada–United States border. The five lakes are Superior, Michigan, Huron, Erie, and Ontario (though hydrologically, Michigan and Huron are a single body of water, joined at the Straits of Mackinac). The Great Lakes Waterway enables modern travel and shipping by water among the lakes. The lakes connect ultimately to the Atlantic Ocean via the Saint Lawrence River as their primary drainage outflow. The lakes are also connected to the Mississippi River basin through the Illinois Waterway.

The Great Lakes are the largest group of freshwater lakes on Earth by total area and the second-largest by total volume. They contain 21% of the world's surface fresh water by volume. The total surface is 94,250 square miles (244,106 km), and the total volume (measured at the low water datum) is 5,439 cubic miles (22,671 km), slightly less than the volume of Lake Baikal (5,666 cu mi or 23,615 km, 22–23% of the world's surface fresh water). Because of their sea-like characteristics, such as rolling waves, sustained winds, strong currents, great depths, and distant horizons, the five Great Lakes have long been called inland seas. Depending on how it is measured, by surface area, either Lake Superior or Lake Michigan–Huron is the second-largest lake in the world and the largest freshwater lake. Lake Michigan is the largest lake, by surface area, that is entirely within one country, the United States.

Illinois (/ˌɪlɪˈnɔɪ/ IL-ih-NOY) is a state in the Midwestern region of the United States. It borders Lake Michigan to its northeast, the Mississippi River to its west, and the Wabash and Ohio rivers to its south. Of the fifty U.S. states, Illinois has the fifth-largest gross domestic product (GDP), the sixth-largest population, and the 25th-most land area. Its capital city is Springfield in the center of the state, and the state's largest city is Chicago in the northeast.

Present-day Illinois was inhabited by Indigenous cultures for thousands of years. The French were the first Europeans to arrive, settling near the Mississippi and Illinois rivers in the 17th century Illinois Country, as part of their sprawling colony of New France. A century later, the revolutionary war Illinois campaign prefigured American involvement in the region. Following U.S. independence in 1783, which made the Mississippi River the national boundary, American settlers began arriving from Kentucky via the Ohio River. Illinois was soon part of the United States' oldest territory, the Northwest Territory, and in 1818 it achieved statehood. The Erie Canal brought increased commercial activity in the Great Lakes, and the invention of the self-scouring steel plow by Illinoisan John Deere turned the state's rich prairie into some of the world's most productive and valuable farmland, attracting immigrant farmers from Germany, Sweden and elsewhere. In the mid-19th century, the Illinois and Michigan Canal and a sprawling railroad network facilitated trade, commerce, and settlement, making the state a transportation hub for the nation, especially in the city of Chicago, which became the world's fastest growing city by the late 19th century. By 1900, the growth of industrial jobs in the northern cities and coal mining in the central and southern areas attracted immigrants from Eastern and Southern Europe. Illinois became one of America's most industrialized states and remains a major manufacturing center. The Great Migration from the South established a large Black community, particularly in Chicago, which became a leading cultural, economic, and population center; its metropolitan area, informally referred to as Chicagoland, holds about 65% of the state's 12.8 million residents.

The Loop is Chicago's central business district and one of the city's 77 municipally recognized community areas. Located at the center of downtown Chicago on the shores of Lake Michigan, it is the second-largest business district in North America, after Midtown Manhattan in New York City. It contains the world headquarters and regional offices of several global and national businesses, retail establishments, restaurants, hotels, museums, theaters, and libraries—as well as many of Chicago's most famous attractions. The district also hosts Chicago's City Hall, the seat of Cook County, offices of the state of Illinois, United States federal offices, and several foreign consulates. The intersection of State Street and Madison Street in the Loop is the origin point for the address system on Chicago's street grid, a grid system that has been adopted by numerous cities worldwide.

The Loop's definition and perceived boundaries have evolved over time. Since the 1920s, the area bounded by the Chicago River to the west and north, Lake Michigan to the east, and Roosevelt Road to the south has been called the Loop. It took its name from a somewhat smaller area, the 35 city blocks bounded on the north by Lake Street, on the west by Wells Street, on the south by Van Buren Street, and on the east by Wabash Avenue—the Union Loop formed by the 'L' in the late 1800s. Similarly, the "South Loop" and the "West Loop" historically referred to areas within the Loop proper, but in the 21st century began to refer to the entire Near South and much of the Near West Sides of the city, respectively.

A lake is often a naturally occurring, relatively large and fixed body of water on or near the Earth's surface. It is localized in a basin or interconnected basins surrounded by dry land. Lakes lie completely on land and are separate from the ocean, although they may be connected with the ocean by rivers. Lakes, like other bodies of water, are part of the water cycle, the processes by which water moves around the Earth. Most lakes are fresh water and account for almost all the world's surface freshwater, but some are salt lakes with salinities even higher than that of seawater. Lakes vary significantly in surface area and volume of water.

Lakes are typically larger and deeper than ponds, which are also water-filled basins on land, although there are no official definitions or scientific criteria distinguishing the two. Lakes are also distinct from lagoons, which are generally shallow tidal pools dammed by sandbars or other material at coastal regions of oceans or large lakes. Most lakes are fed by springs, and both fed and drained by creeks and rivers, but some lakes are endorheic without any outflow, while volcanic lakes are filled directly by precipitation runoffs and do not have any inflow streams.

Lake Huron (/ˈhjʊərɒn, -ən/ HURE-on, -⁠ən) is one of the five Great Lakes of North America. It is shared on the north and east by the Canadian province of Ontario and on the south and west by the U.S. state of Michigan. The name of the lake is derived from early French explorers who named it for the indigenous people they knew as Huron (Wyandot) inhabiting the region.Hydrologically, Lake Huron comprises the eastern portion of Lake Michigan–Huron, having the same surface elevation as Lake Michigan, to which it is connected by the 5-mile-wide (8.0 km), 20-fathom-deep (120 ft; 37 m) Straits of Mackinac. Combined, Lake Michigan–Huron is the largest freshwater lake by area in the world. The Huronian glaciation was named from evidence collected from the Lake Huron region. The northern parts of the lake include the North Channel and Georgian Bay. Saginaw Bay is located in the southwest corner of the lake. The main inlet is the St. Marys River from Lake Superior, and the main outlet is through the St. Clair River toward Lake Erie. Lake Huron has a fairly large drainage basin covering parts of Michigan and Ontario. Water flows through Lake Huron faster than the other Great Lakes with a retention time of only 22 years.

Lake Michigan–Huron (also Huron–Michigan) is the body of water combining Lake Michigan and Lake Huron, which are joined through the 5-mile-wide (8.0 km), 295-foot-deep (90 m), open-water Straits of Mackinac. Huron and Michigan are hydrologically a single lake because the flow of water through the straits keeps their water levels in overall equilibrium. Although the flow is generally eastward, the water moves in either direction depending on local conditions. Combined, Lake Michigan–Huron is the largest freshwater lake by area in the world. Lake Superior is larger than either individually, so it is counted as the largest of the Great Lakes when Lake Michigan and Lake Huron are considered separately.

The Straits of Mackinac (/ˈmækənɔː/ MAK-ə-naw; French: Détroit de Mackinac) are the short waterways between the U.S. state of Michigan's Upper and Lower Peninsulas, traversed by the Mackinac Bridge. The main strait is 3+1⁄2 miles (5.6 kilometers) wide with a maximum depth of 295 feet (90 meters; 49 fathoms), and connects the Great Lakes of Lake Michigan and Lake Huron. Given the large size and configuration of the straits, hydrologically, the two connected lakes are one body of water, studied as Lake Michigan–Huron. Historically, the native Odawa people called the region around the Straits Michilimackinac.

Three islands form the eastern edge of the Straits of Mackinac; two are populated—Bois Blanc Island and Mackinac Island, while the third, Round Island, is uninhabited and a designated wilderness area. The Straits of Mackinac are major shipping lanes, providing passage for raw materials and finished goods and connecting, for instance, the iron mines of Minnesota to the steel mills of Gary, Indiana. Before the railroads reached Chicago from the east, most immigrants arrived in the Midwest and Great Plains by ships on the Great Lakes. The straits are five miles (8 km) wide at their narrowest point, where they are spanned by the Mackinac Bridge. Before the bridge was built, car ferries transported vehicles across the straits. Today passenger-only ferries carry people to Mackinac Island, which does not permit cars. Visitors can take their vehicles on a car ferry to Bois Blanc Island.

The Illinois Waterway system consists of 336 miles (541 km) of navigable water from the mouth of the Calumet River at Chicago to the mouth of the Illinois River at Grafton, Illinois. Based primarily on the Illinois River, it is a system of rivers, lakes, and canals that provide a commercial shipping connection from the Great Lakes to the Gulf of Mexico via the Illinois and Mississippi rivers.

The Illinois and Michigan Canal (I&M) opened in 1848. In 1900, the Chicago Sanitary and Ship Canal replaced the I&M and reversed the flow of the Chicago River so it no longer flowed into Lake Michigan. The United States Army Corps of Engineers maintains a 9-foot-deep (2.7 m) navigation channel in the waterway. The waterway's complex northern section is referred to in various contexts for study and management as the Chicago Area Waterway System (CAWS).