Illinois (IL) is located in the American Midwest. Its diversified economy relies on industry, agriculture, and financial services. Although the state capital of Illinois is Springfield, the largest and most well-known city is Chicago. It was in Chicago that the world’s first skyscraper, the Home Insurance Building, opened in 1885. At the time of its opening, the building had 10 floors (two more were added later) and measured 138.0 ft.
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Table of Contents
Basic Information
Name Illinois Abbreviation IL Capital Springfield Largest city Chicago (Population: 2 664 452) Current time 18:52 Time zone CST (UTC-6), the state observes daylight saving time CDT (UTC-5) Population 12,813,469 (#6 most populous US state) Area 57,914 sqmi (#25 largest US state) Admitted to the Union December 3, 1818 (#21 state to join) ⭐ Capital of Illinois
The capital of the state of Illinois is Springfield, which was founded in 1821 and was originally named Calhoun in honor of South Carolina Senator John Caldwell Calhoun. Springfield became the capital of Illinois in 1839.
🏙️ Largest City in Illinois
The largest city in Illinois is Chicago, home to 2,664,452 residents in 2023. Aurora ranks second with a population of 177,563, followed by Joliet with 150,489 residents.
🕒 Time in Illinois
The current time in Chicago is 18:52. The entire state of Illinois observes Central Standard Time (CST, UTC-6) and switches to Daylight Saving Time (CDT, UTC-5) from March to November.
🧑🤝🧑 Population of Illinois
In 2023, Illinois had a population of 12,813,469, making it the sixth most populous state in the USA.
📍 Area of Illinois
The total area of the state of Illinois is 57,914 sqmi, of which 55,586 sqmi is land and 2,309 sqmi is water. Illinois is the 25th largest state in the USA.
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Fun Facts About the State of Illinois
🧩 Which States Border Illinois
Illinois shares land borders with five different U.S. states. To the southwest lies Missouri, to the northwest Iowa, to the north Wisconsin, to the east Indiana, and to the south Kentucky. In addition, Illinois has a shoreline on Lake Michigan, where Illinois shares a water boundary with the state of Michigan. Worth mentioning is also the enclave of Kaskaskia, a small area surrounded by the state of Missouri.
📅 Date Illinois Joined the Union
Illinois joined the Union on December 3, 1818, becoming the 21st state. Before statehood, it was part of the Illinois Territory.
📛 Nickname of the State of Illinois
Illinois takes pride in the 16th President of the United States, Abraham Lincoln, who lived in the state for many years. As such, Illinois adopted the official slogan “Land of Lincoln”, which is used, among other places, on vehicle license plates.
The unofficial nickname of Illinois is “The Prairie State”, referencing the expansive prairie plains that are characteristic of the region.
⛰️ Highest Point in the State of Illinois
The highest point in Illinois is the modest hill Charles Mound, which stands at only 1,235 ft and is located near the state’s border with Wisconsin.
🏞️ Rivers in Illinois
The longest river in Illinois is the Mississippi River, with a total length across all states of 2,318 mi. It is followed by the Ohio River (981 mi), the Wabash River (503 mi), the Illinois River (332 mi), and the Rock River (299 mi).
🎓 Universities in Illinois
The largest university in the state is the University of Illinois Urbana-Champaign, founded in 1867 and currently attended by around 57,000 students. In second place is the University of Illinois Chicago, with approximately 34,000 students, followed by Northwestern University, with about 23,000 enrolled students.
✉️ ZIP Codes in Illinois
The state of Illinois is assigned ZIP codes ranging from 600xx–620xx and 622xx–629xx. For more information, see the article ZIP Codes in the USA, or look up a specific ZIP code on the U.S. Postal Service website.
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Weather in Illinois
The best time to visit Illinois is in the fall, when temperatures are pleasant and rainfall is lower compared to spring and summer.
Spring in Illinois brings gradually improving weather, with temperatures typically ranging between 50 °F and 68 °F. Especially in April and May, frequent rain showers should be expected, with occasional thunderstorms accompanied by strong winds and hail.
Summer in Illinois is hot and humid, with temperatures usually reaching between 77 °F and 86 °F. High humidity can be unpleasant, and in June in particular, frequent rain showers may cause flash flooding.
Fall in Illinois is more comfortable, with typical temperatures ranging from 50 °F to 59 °F. Rain is less common compared to other months, creating ideal conditions for travel and outdoor exploration.
Winters in Illinois are very cold, with temperatures dropping below freezing to between 32 °F and 14 °F. Snowfall is common, and in January and February, monthly snow accumulation can reach up to 30 cm. Strong winds can further lower the perceived temperature.
🌡️ Average Temperatures and Precipitation in Illinois
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What to See in Illinois
1️⃣ Millennium Park in Chicago
Millennium Park is one of the most famous attractions in the state, drawing millions of visitors every year. The park is renowned for its art installations, the most iconic of which is the stainless steel Cloud Gate sculpture. Photos of its reflective surface with the city’s skyscrapers are among the most recognizable images of Chicago. The park, which is free to enter, frequently hosts cultural and social events outdoors.
2️⃣ Six Flags Great America Amusement Park
Six Flags Great America is among the best amusement parks in the USA. Visitors can enjoy around a hundred attractions, including more than ten thrilling roller coasters. On hot summer days, the adjacent Hurricane Harbor water park offers a refreshing escape. The park provides full-day entertainment for families with children as well as groups of friends.
3️⃣ Willis Tower Skyscraper in Chicago
Willis Tower is a 1,450 ft tall skyscraper in Chicago, known as the Sears Tower until 2009 after the retail company that built it in the 1970s. The building’s Skydeck on the 103rd floor is open to visitors and offers spectacular views of the city and surrounding landscape.
On clear days, visibility can extend up to 50 mi. A popular attraction in the tower is The Ledge, a glass balcony that juts out from the building, allowing visitors to look straight down at the street below.
4️⃣ Route 66 Museum
The famous Route 66, which passed through eight U.S. states including Illinois, is honored at a museum in the town of Pontiac. The museum houses an extensive collection of photos, artifacts, and other memorabilia related to the legendary highway’s history. Visitors can learn how Route 66 influenced American culture and view historic vehicles that once traveled its length.
5️⃣ Chicago Museum of Science and Industry
The Museum of Science and Industry in Chicago is one of the largest of its kind in the world. Visitors can explore interactive exhibits focused on science, technology, and industry. A popular highlight is the German U-505 submarine, which has been part of the museum’s collection since 1954. Some exhibits are rotated regularly, and the museum also hosts recurring workshops.
6️⃣ Magnificent Mile Shopping Boulevard
If New York has its famous Fifth Avenue, Chicago boasts the Magnificent Mile. This renowned downtown street is lined with luxury shops and designer boutiques, complemented by upscale restaurants and hotels.
Some buildings are architectural landmarks in their own right. Notable examples include the neo-Gothic Tribune Tower from 1923 and the Wrigley Building, once home to the famous chewing gum manufacturer.
7️⃣ Shedd Aquarium in Chicago
Shedd Aquarium in Chicago is home to thousands of marine and freshwater species, making it one of the largest aquatic centers in the United States. Behind the thick glass tanks, visitors can observe dolphins, sharks, penguins, turtles, and other creatures from oceans, rivers, and lakes. The aquarium features interactive exhibits and educational programs focused on marine conservation. Shedd Aquarium is a fun destination for families with children of all ages.
8️⃣ Navy Pier in Chicago
Once a dock for naval ships, Navy Pier is now one of Chicago’s top tourist attractions, offering a variety of entertainment options including a Ferris wheel and restaurants. During the summer season, it is a popular venue for concerts and theatrical performances. Visitors can enjoy boat cruises on Lake Michigan or simply take in the panoramic views of the Chicago skyline.
9️⃣ Illinois State Capitol Building
Located in the state capital of Springfield, the Illinois State Capitol serves as the seat of government and stands as one of the most significant historic buildings in the state. Constructed between 1868 and 1888, the Capitol showcases stunning Neo-Renaissance architecture with elements of the Second Empire style. Guided tours are available for those interested in exploring the legislative chambers and learning about the building’s history.
🔟 The Art Institute of Chicago
The Art Institute of Chicago is one of the world’s most prestigious art museums. Its collection includes thousands of works, with a large portion dedicated to Impressionist and Post-Impressionist paintings by artists such as French painter Claude Monet, Dutch artist Vincent van Gogh, and French painter Georges Seurat. Some exhibits are periodically rotated.
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Largest Cities in Illinois
The table shows the ten largest cities in the state of Illinois in 2025, based on data from the federal agency United States Census Bureau, whose primary role is conducting population censuses.
City County Population 1 Chicago Cook, DuPage 2,664,452 Map of Chicago 2 Aurora DuPage, Kane, Kendall, Will 177,563 Map of Aurora 3 Joliet Will, Kendall 150,489 Map of Joliet 4 Naperville DuPage, Will 150,245 Map of Naperville 5 Rockford Winnebago, Ogle 146,120 Map of Rockford 6 Elgin Kane, Cook 113,310 Map of Elgin 7 Springfield Sangamon 112,544 Map of Springfield 8 Peoria Peoria 110,460 Map of Peoria 9 Champaign Champaign 89,189 Map of Champaign 10 Waukegan Lake 87,642 Map of Waukegan -
Sports Teams in Illinois
🏒 Hockey (NHL)
The only team from Illinois in the prestigious NHL is the Chicago Blackhawks, founded in 1926. The team competes in the Central Division of the Western Conference. Home games are played at the United Center in Chicago, and the team colors are red, white, and black.
🏈 American Football (NFL)
The sole NFL team from Illinois is the Chicago Bears, who played in the league’s inaugural 1920 season. The team is part of the NFC North Division and plays its home games at Soldier Field in Chicago. The Bears’ official colors are navy blue, orange, and white.
🏀 Basketball (NBA)
The only NBA team from Illinois is the Chicago Bulls from the Central Division of the Eastern Conference. The team plays its home games at the United Center in Chicago. The team colors are red, black, and white, and the Chicago Bulls played their first NBA season in 1966.
⚾ Baseball (MLB)
Illinois is home to two teams that compete in Major League Baseball (MLB).
The Chicago Cubs have been part of the National League since 1876 and are currently in its Central Division. The team colors are blue, red, and white. The Cubs play their home games at Wrigley Field in Chicago.
The second team is the Chicago White Sox, who began playing baseball in 1901. They are in the Central Division of the American League and host their home games at Guaranteed Rate Field in Chicago. The White Sox team colors are black, silver, and white.
⚽ Soccer (MLS)
Since the 1998 season, the Chicago Fire FC has played in Major League Soccer (MLS), joining the Eastern Conference. The team colors are red, blue, navy, and white, and all home games are held at Soldier Field in Chicago.
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State Symbols of Illinois
Since joining the Union in 1818, the state of Illinois has adopted a number of official state symbols. Below are just a few of them.
Illinois State Flag
The Illinois state flag features the state seal on a white background, accompanied by the name of the state. The current design has been in use since September 17, 1969, when a slight graphical modification of the seal was made and the state name was added.
Illinois State Seal
The central motif of the seal is a bald eagle standing on a rock, holding a shield in its talons and a banner with the state motto in its beak. The shield displays thirteen stars and thirteen stripes, representing the original thirteen states of the Union. The seal was designed by Sharon Tyndale, former Illinois Secretary of State from 1865 to 1869.
State Flower
Since 1908, the official state flower has been the common blue violet (Viola sororia). Around 30 species of this plant grow throughout the state.
State Bird
The northern cardinal (Cardinalis cardinalis) was designated a state symbol in 1929. It became a common sight in Illinois after 1900.
State Fish
In 1986, legislation recognized the bluegill (Lepomis macrochirus) as a state symbol. This fish inhabits waters throughout Illinois.
State Snack
Illinois is home to around 330 farms dedicated to growing corn for popcorn production. Since 2004, popcorn has been the official state snack.
State Mineral
Fluorite has been the official state mineral since 1965. The most significant deposits are located in southern Illinois, near the city of Rosiclare and the village of Cave-In-Rock.
State Wildflower
In 2017, the wildflower milkweed (Asclepias spp.) was added to the list of Illinois state symbols.
State Vegetable
A 2015 law designated sweet corn as the official state vegetable. This crop is commonly grown throughout the state.
State Snake
Since 2022, the official state snake has been the eastern milksnake (Lampropeltis triangulum triangulum), a reddish-brown snake with white and black banding, typically measuring 60 cm to 180 cm.
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