Illinois is a state in the Midwestern region of the United States. It has the fifth largest gross domestic product (GDP), the sixth largest population, and the 25th largest land area of all U.S. states. Illinois has been noted as a microcosm of the entire United States.[7] With Chicago in northeastern Illinois, small industrial cities, and immense agricultural productivity in the north and center of the state, and natural resources such as coal, timber, and petroleum in the south, Illinois has a diverse economic base, and is a major transportation hub.

The Port of Chicago connects the state to international ports via two main routes: from the Great Lakes, via the Saint Lawrence Seaway, to the Atlantic Ocean and from the Great Lakes to the Mississippi River, via the Illinois River, through the Illinois Waterway. The Mississippi River, the Ohio River, and the Wabash River form parts of the boundaries of Illinois. For decades, Chicago’s O’Hare International Airport has been ranked as one of the world’s busiest airports. Illinois has long had a reputation as a bellwether both in social and cultural terms and, through the 1980s, in politics.

The capital of Illinois is Springfield, which is in the central part of the state. Although today Illinois’s largest population center is in its northeast, the state’s European population grew first in the west as the French settled lands near the Mississippi River, when the region was known as Illinois Country and was part of New France.

Following the American Revolutionary War, American settlers began arriving from Kentucky in the 1780s via the Ohio River, and the population grew from south to north. In 1818, Illinois achieved statehood.

Following increased commercial activity in the Great Lakes after the construction of the Erie Canal, Chicago was incorporated in the 1830s on the banks of the Chicago River at one of the few natural harbors on the southern section of Lake Michigan. John Deere’s invention of the self-scouring steel plow turned Illinois’s rich prairie into some of the world’s most productive and valuable farmland, attracting immigrant farmers from Germany and Sweden.

The Illinois and Michigan Canal (1848) made transportation between the Great Lakes and the Mississippi River valley faster and cheaper, and new railroads carried immigrants to new homes in the country’s west and shipped commodity crops to the nation’s east. The state became a transportation hub for the nation.

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 was an important manufacturing center during both world wars. The Great Migration from the South established a large community of African Americans in the state, including Chicago, who founded the city’s famous jazz and blues cultures.

Chicago, the center of the Chicago Metropolitan Area, is recognized as a global city. Chicagoland, Chicago’s metropolitan area, encompasses about 65% of the state’s population. The most populous metropolitan areas outside the Chicago area include, Metro East (of Greater St. Louis), Peoria and Rockford.

CLIMATE

Illinois has a climate that varies widely throughout the year. Because of its nearly 400-mile distance between its northernmost and southernmost extremes, as well as its mid-continental situation, most of Illinois has a humid continental climate with hot, humid summers and cold winters. The southern part of the state, from about Carbondale southward, has a humid subtropical climate, with more moderate winters.

Average yearly precipitation for Illinois varies from just over 48 inches (1,219 mm) at the southern tip to around 35 inches (889 mm) in the northern portion of the state. Normal annual snowfall exceeds 38 inches (965 mm) in the Chicago area, while the southern portion of the state normally receives less than 14 inches (356 mm). The all-time high temperature was 117 °F (47 °C), recorded on July 14, 1954, at East St. Louis, and the all-time low temperature was −38 °F (−39 °C), recorded on January 31, 2019, during the January 2019 North American cold wave at a weather station near Mount Carroll, and confirmed on March 5, 2019.

This followed the previous record of −36 °F (−38 °C) recorded on January 5, 1999, near Conger Ville. Prior to the Mount Carroll record, a temperature of −37 °F (−38 °C) was recorded on January 15, 2009, at Rochelle, but at a weather station not subjected to the same quality control as official records.

Illinois averages approximately 51 days of thunderstorm activity a year, which ranks somewhat above average in the number of thunderstorm days for the United States. Illinois is vulnerable to tornadoes, with an average of 35 occurring annually, which puts much of the state at around five tornadoes per 10,000 square miles (30,000 km2) annually. While tornadoes are no more powerful in Illinois than other states, some of Tornado Alley’s deadliest tornadoes on record have occurred in the state. The Tri-State Tornado of 1925 killed 695 people in three states; 613 of the victims died in Illinois.