Marion is a city in and the county seat of Williamson County, Illinois, United States. The population was 16,855 according to the 2020 census. It is part of a dispersed urban area that developed out of early 20th-century coal fields.
Marion serves as the largest retail trade center in Southern Illinois with its central location along Interstate 57 and Illinois Route 13. The city is part of the Marion-Herrin micropolitan area and is a part of the Carbondale-Marion-Herrin, Illinois combined statistical area with 123,272 residents, the sixth-most populous Combined statistical area in Illinois.
Indigenous nations that have been in this region for a very long time include:
𐓏𐒰𐓓𐒰𐓓𐒷 𐒼𐓂𐓊𐒻 𐓆𐒻𐒿𐒷 𐓀𐒰^𐓓𐒰^(Osage)
Following the creation of Williamson County out of the south half of Franklin County by the Illinois General Assembly, three commissioners appointed by the colonial lawmakers met at Bainbridge, Illinois, on August 19, 1839, for the purpose of locating a new county seat as close to the center of the county as possible. The next day, August 20, they laid out a town of 20 acres (81,000 m2) with a public square about one-quarter of a mile east of the county's center, but a point on top of a slight hill of 448 feet (137 m) above sea level. The site sat in a small open grassland known as Poor Prairie. For a name, they chose Marion to honor American Revolutionary War hero Gen. Francis "Swamp Fox" Marion.
William and Bethany Benson had entered the quarter-quarter section of land that contained the future site of Marion just the previous year on September 8, 1838. He had lived in the county at least since 1817, and was the first settler to enter land in Poor Prairie. At the time the commissioners platted Marion, he had a small crop of corn and wheat growing over what became the public square.
The Williamson County Court organized in Marion on October 7, 1839, at the Benson log cabin. Overflow crowds had to use pumpkins for stools. The federal government established a post office at Marion on January 30, 1840, and the legislature incorporated the community as a city on February 24, 1841.
On May 29, 1982, one of the larger tornadoes in Illinois history, rated F4, hit the city of Marion and Williamson County. Ten people died and 181 people were injured after this tornado ripped across a 17-mile (27 km) stretch. The Shawnee Village apartment complex was destroyed, and the Marion Ford-Mercury dealership sustained heavy damage. This tornado caused between $85 million and $100 million in damages. A memorial to the ten people who perished that day was later erected on the south side of Tower Square Plaza.
An EF4 tornado struck to the south of Marion on May 16, 2025 with wind speeds reaching 190 mph (310 km/h). The tornado caused seven injuries but no fatalities. This tornado prompted a tornado emergency.
Marion is in central Williamson County, with a narrow strip of city limits extending south beyond Creal Springs to the valley of Sugar Creek in Johnson County. Marion is 44 miles (71 km) south of Mount Vernon, Illinois, and 57 miles (92 km) north of Paducah, Kentucky. Carbondale is 17 miles (27 km) to the west, and Harrisburg is 22 miles (35 km) to the east.
According to the 2010 census, Marion has a total area of 16.217 square miles (42.00 km2), of which 15.99 square miles (41.41 km2) (or 98.6%) is land and 0.227 square miles (0.59 km2) (or 1.4%) is water.
As of the 2020 census, Marion had a population of 16,855. The population density was 1,171.1 inhabitants per square mile. The median age was 41.2 years. 21.2% of residents were under the age of 18 and 22.0% of residents were 65 years of age or older. For every 100 females there were 91.7 males, and for every 100 females age 18 and over there were 88.2 males age 18 and over.
99.2% of residents lived in urban areas, while 0.8% lived in rural areas.
There were 7,547 households in Marion, of which 25.8% had children under the age of 18 living in them. Of all households, 37.8% were married-couple households, 20.7% were households with a male householder and no spouse or partner present, and 34.3% were households with a female householder and no spouse or partner present. About 37.8% of all households were made up of individuals and 17.7% had someone living alone who was 65 years of age or older.
There were 8,644 housing units, of which 12.7% were vacant. The homeowner vacancy rate was 4.3% and the rental vacancy rate was 16.6%.
The median household income in the Marion city, IL is $54,052 and the median house value is $143,600. The per capita income for the city was $36,935. About 15.0% of the population were living below the poverty line. The region has a civilian labor force of 7,866 with a participation rate of 57.8%. Of individuals 25 to 64 in the Marion city, IL, 30.1% have a bachelor's degree or higher.
As of 2023Q4, total employment for the Marion city, IL was 18,253 (based on a four-quarter moving average). Over the year ending 2023Q4, employment increased 2.1% in the region.
As of 2022, Marion has a Veteran population of 1,544 persons.