Illinois is dominated by Chicago — America's third-largest city, on Lake Michigan, with the Sears (Willis) Tower and a deep architectural and jazz heritage. The state is also Abraham Lincoln's adopted home.
Geography & climate
Illinois lies in the Midwest of the United States, set at approximately 40°N, 89°W and falling within a temperate climate band. The state covers around 149,998 km² of land, with topography that runs from coastal lowlands and river basins to interior plains and (where present) mountain ranges. Local weather, growing seasons and outdoor recreation in Illinois all flow from this geographic profile.
Capital, principal city & population
The capital of Illinois is Springfield, where the legislature, governor’s office and state supreme court are based. The largest city by population is Chicago, often the economic and cultural anchor of the state. Total population sits at around 12.5M, distributed across metropolitan areas, smaller cities, and rural counties — each with its own dialect, demographics and economic character.
Statehood & history
Illinois was admitted to the Union in 1818 as the 21st state. The path to admission typically passed through territorial status, an enabling act of Congress and the drafting of a state constitution. Each generation since has added its layer to the state’s political and cultural identity — from frontier settlement and industrial expansion to the civic and demographic shifts of the modern era.
Symbols & emblems
Illinois is nicknamed “The Prairie State”, with the state motto State Sovereignty, National Union. The state seal, flag and coat of arms each carry historic meaning, often referencing founding settlers, native communities, agricultural roots or pivotal episodes of state history. State legislatures have additionally adopted official symbols — a state bird, flower, tree, song, fossil and more — chosen by lawmakers (and sometimes by schoolchildren) to celebrate distinctive elements of the state’s natural and cultural heritage.
Economy & industry
The economy of Illinois is shaped by its geography, infrastructure and population centres. Major sectors typically span agriculture, manufacturing, energy or natural resources, services, tourism and (in metropolitan corridors) finance and technology. Federal facilities, military bases and research institutions can also be substantial regional employers in Illinois.
Travel, food & culture
For visitors, Illinois offers a mix of urban culture (museums, music venues, sports teams, cuisine) and outdoor experience (state parks, trails, coastline or mountains, depending on the geography). Regional foodways, festivals and dialects make travel between counties feel meaningfully different — even short drives across Illinois can shift the cultural landscape noticeably.
By the numbers
Sort or filter the table to find the values you need at a glance.
| Field | Value | Note |
|---|---|---|
| Abbreviation | IL | two-letter postal code |
| Capital | Springfield | — |
| Largest city | Chicago | — |
| US region | Midwest | — |
| Population | 12.5M | people |
| Area | 149,998 | km² |
| Statehood | 1818 | year admitted |
| Admission order | 21 | order joining the Union |
| Nickname | The Prairie State | — |
| Motto | State Sovereignty, National Union | — |
| Latitude | 40 | degrees |
| Longitude | -89 | degrees |
Did you know?
The original Sears Tower in Chicago was the world's tallest building from 1973 until 1998, and is still the tallest in the Western Hemisphere.
