The St. Louis metropolitan area is the 21st largest in the United States with a population of 2.8 million. The bi-state metropolitan area includes seven counties in Missouri and eight in Illinois, for a total of 15 counties. The St. Louis area spans both sides of the Missouri and Mississippi rivers, with a footprint that extends into both Missouri and Illinois.

In addition to offering access to a population with an extensive range of skill sets and educational backgrounds, each county also affords St. Louis area residents excellent access to a range of cultural and recreational assets.

Household Types

St. Louis, MO-IL MSA

United States

% of total

% of total

Total households




Average household size



Average family size




St. Louis, MO-IL MSA

United States

Median household income



Per capita income



Population Demographics By Age Distribution


St. Louis, MO-IL MSA


Under 5 years



5 to 14 years



15 to 24 years



25 to 34 years



35 to 44 years



45 to 54 years



55 to 64 years



65 years and over



Source: "American Community Survey 2017" U.S. Census Bureau, 2017.

The St. Louis metropolitan area has enjoyed consistent population growth.  The following are brief descriptions of our 15 counties.


Illinois Counties:

Bond County, IL
Bond County is one of the two easternmost counties in the metropolitan area, with a population of 17,137. Although agriculture dominates the economy, Carlyle Lake is bordered by a variety of resort, hunting, and fishing businesses. Click here for county map.

Calhoun County, IL
Calhoun County has a population of 4,962 and is located on a peninsula between the Mississippi and Illinois Rivers. Ferries are the major mode of transportation, and this county features many historic sites and nature areas. Click here for county map.  

Clinton County, IL
Just over 37,858 people reside in primarily rural Clinton County, with some resort-based industry surrounding the southern half of Carlyle Lake. Illinois State Highway 50 and parallel railroad tracks bisect the county east to west. Click here for county map.

Jersey County, IL
Jersey County, population 22,441is on the Great River Road, which winds alongside the Mississippi River. The county is largely rural, with small towns dispersed throughout. Principia College, overlooking the Mississippi, is in the picturesque village of Elsah. Click here for county map.

Macoupin County, IL
The northernmost county in the metro area is Macoupin County with a population of 46,482. Interstate 55 cuts across the southeastern edge of this agricultural county. The county seat is Carlinville. Click here for county map.

Madison County, IL
The Mississippi River forms the western border of Madison County, whose population is 266,759. Much of the population and employment is centered in the county seat, Edwardsville, and other cities including Alton, Collinsville, and Granite City. Click here for county map.

Monroe County, IL
Monroe County's major industry is agriculture. The county has easy access to the City of St. Louis via Interstate 255 and the Jefferson Barracks Bridge. Waterloo serves as the county seat for the 33,703 residents of the area. Click here for county map.

St. Clair County, IL
Across the Mississippi River from the City of St. Louis, St. Clair County has a population of 265,569. Belleville is the county seat. The county is home to both MidAmerica St. Louis Airport and Scott Air Force Base. Click here for county map.

Missouri Counties:

Franklin County, MO
Union is the county seat of Franklin County, which has an estimated population of 102,084. Manufacturing is the dominant industry, primarily in the city of Washington. Small farms and wineries also contribute to the economy. Click here for county map.

Jefferson County, MO
Jefferson County, bordered on the east by the Mississippi River, has experienced rapid growth recently to 222,453. Manufacturing, construction, and business services are the major industries. Interstate 55 connects the county to Memphis, the City of St. Louis, and Chicago. Click here for county map.

Lincoln County, MO
Lincoln County, whose county seat is Troy, is north of Warren and St. Charles Counties with the Mississippi River to the east. Manufacturing and service industries are major employers. The county is one of the fastest growing in the country with a population of 54,286, which increased by more than 37.9% from 2000 to 2008. Click here for county map.

St. Charles County, MO
St. Charles County, with a population of 379,856, has been one of the fastest-growing counties in the country for decades. The county features a cross-section of industry, as well as extensive retail and some agriculture. St. Charles County has two small airports and two ferries that cross the Mississippi River. Click here for county map.

City of St. Louis, MO
Home to an estimated 316,030 people within 61.9 square miles, the City of St. Louis is the most densely populated and industrial county in the metropolitan area. Manufacturing and corporate headquarters have a strong presence. Interstates 55, 70, 64, and 44 all pass through the city. Click here for county map.

St. Louis County, MO
With 1,000,560 residents, St. Louis County is the most populous of the metropolitan-area counties. There is still some agriculture along the Missouri River in the north, but overall the area is thoroughly suburban with many corporate offices and service businesses. Clayton, the county seat, is often called the St. Louis area's "second downtown". Click here for county map.

Warren County, MO
Warren County, population 33,290, is primarily agricultural. The Missouri River forms the southern border; Interstate 70 crosses the county east to west. Warrenton is the county seat. Click here for county map

Source: "Estimates of Resident Population Change and Rankings: July 1,2016 to July 1 2017", U.S. Census Bureau. Note: Population estimates as of July 1, 2017.