St. Louis County, Missouri

St. Louis County is a county in Missouri, United States, wrapped around the western, northern and southern edges of the independent City of St. Louis. It had a population of 1,004,125 at the 2020 census, an estimated 990,911 by 2025, and covers 508 square miles (1,316 km2) centred near 38°38′N 90°26′W.

Clayton is the county seat; its postal code is 63105. The county holds about 88 incorporated cities, towns and villages plus a handful of unincorporated communities, and it runs on Central time. Its FIPS code is 29189.

Towns & Villages in St. Louis County

St. Louis County is one of the most municipally fragmented counties in the country: roughly 88 incorporated places, most under five square miles, sit inside its 508 square miles, alongside a smaller stretch of unincorporated land. The table below lists the 21 largest by population, with type, 2020 census population and ZIP code where confirmed; a fuller list of the remaining smaller cities and villages follows.

Beyond these 21, roughly 67 more incorporated places share the county, most with populations under 8,000: Brentwood, Richmond Heights, Olivette, Glendale, Frontenac, Sunset Hills, Manchester, Fenton, Eureka, Maplewood, Rock Hill, Berkeley, Normandy, Pagedale, Black Jack, Pine Lawn, Wellston and dozens of smaller villages, several under a few hundred residents (Champ, Huntleigh, Grantwood Village). Several are legally villages rather than cities or towns under Missouri law; this table groups them under “City” for consistency, since the distinction is administrative rather than a difference in character.

The county’s most-searched confusable pair sits at its eastern edge: the City of St. Louis is an independent city, not part of St. Louis County. The two split administratively in 1876 — a separation locally called the Great Divorce — and the city has run its own government ever since. A second county shares the exact name: St. Louis County, Minnesota, home to Duluth, is a different jurisdiction more than 500 miles north.

ZIP Codes

• 63105 — Clayton (also serves Ladue’s eastern edge)
• 63005 — Chesterfield (also serves Wildwood’s northern neighborhoods)
• 63042 — Hazelwood (also serves Berkeley)
• 63043 — Maryland Heights
• 63044 — Bridgeton
• 63119 — Webster Groves (also serves Rock Hill)
• 63123 — Affton
• 63124 — Ladue (also serves Frontenac)
• 63126 — Crestwood (also serves Sappington)
• 63131 — Town and Country (also serves Des Peres)
• 63135 — Ferguson
• 63136 — Jennings (also serves north county unincorporated areas)
• 63141 — Creve Coeur (also serves Town and Country’s western edge)

Several small villages, including Champ, Huntleigh and Grantwood Village, have no ZIP code of their own and are served by the postal code of the larger city that surrounds them.

Geography

The county’s boundaries are almost entirely rivers: the Missouri River forms the northern edge, the Meramec River the southern edge, and the Mississippi River, along with the City of St. Louis, the eastern edge. Terrain rises from river-bottom floodplain in the north and east to rolling upland in the west, where Wildwood and Chesterfield sit on higher ground above the Missouri River valley. The Meramec River corridor along the southern border includes Castlewood State Park and several county parks with wooded bluffs.

St. Louis County borders St. Charles County to the north and northwest across the Missouri River, Jefferson County to the south across the Meramec River, and Franklin County to the southwest. The independent City of St. Louis, not itself a county, borders it directly to the east. Across the Mississippi River to the east lie Madison County and St. Clair County, Illinois.

Demographics

St. Louis County counted 1,004,125 residents at the 2020 census, Missouri’s most populous county, with an estimated 990,911 residents by 2025 — a slight decline typical of older, largely built-out inner suburbs. Florissant, at 52,533, and Chesterfield, at 49,999, are the two largest communities; Clayton, the seat, has 17,355. Land area is 508 square miles, giving a population density of roughly 1,950 people per square mile, among the densest in Missouri outside the city itself.

Economy & Local Life

Healthcare and professional services anchor the county’s economy. BJC HealthCare and Mercy operate major hospital campuses in Clayton, Creve Coeur and Chesterfield; Centene, Edward Jones and Wells Fargo Advisors are headquartered in or near Clayton and Des Peres. Boeing Defense, Space & Security runs a large manufacturing complex in Hazelwood and Berkeley, near Lambert-St. Louis International Airport, employing several thousand workers. Retail centers around West County Center in Des Peres and the Chesterfield commercial corridor along I-64. Kirkwood hosts the Greentree Festival every September, one of the county’s longest-running community events.

History

St. Louis County was organized on October 1, 1812, one of the original districts of Missouri Territory, and takes its name, like the city, from Louis IX of France. Until 1876 the City of St. Louis was legally part of the county; that year city voters approved a charter separating city government from county government, a decision now remembered locally as the Great Divorce. The city never rejoined, and the county grew as a separate suburban jurisdiction through the 20th century, especially after 1950.

On August 9, 2014, Ferguson police officer Darren Wilson fatally shot 18-year-old Michael Brown, an unarmed Black resident, following a street confrontation. The shooting triggered weeks of protests and unrest in Ferguson and drew national attention to policing in the county’s smaller municipalities. A U.S. Department of Justice investigation later found the shooting itself did not warrant federal charges but documented a pattern of unconstitutional policing and revenue-driven municipal court practices in Ferguson, prompting a federal consent decree.

Getting There

Interstates 70, 44, 64 and 270 all cross the county, along with I-170 and I-255; I-270 forms a beltway around the northern, western and southern edges. Lambert-St. Louis International Airport sits inside the county itself, near Bridgeton and Berkeley.

• Downtown St. Louis (City of St. Louis) — adjacent, borders the county directly to the east
• Clayton — 8 miles west of downtown St. Louis
• St. Charles — 12 miles northwest of Clayton, across the Missouri River
• Fenton — 15 miles southwest of Clayton, along the Meramec River

The nearest Amtrak station is the Gateway Multimodal Transportation Center in downtown St. Louis, just east of the county line.

Frequently Asked Questions

Where is St. Louis County?
It surrounds the independent City of St. Louis on the west, north and south, in eastern Missouri along the Mississippi, Missouri and Meramec rivers.

What is the population of St. Louis County?
1,004,125 at the 2020 census, an estimated 990,911 by 2025 — the most populous county in Missouri.

How big is St. Louis County?
508 square miles of land and about 15 square miles of water, 523 square miles total.

What is the county seat of St. Louis County?
Clayton, ZIP code 63105.

Is the City of St. Louis part of St. Louis County?
No. The city separated from the county in 1876 and has run as an independent city ever since; it is not part of any county.

How many towns and cities are in St. Louis County?
About 88 incorporated municipalities, from Florissant (52,533 people) down to villages of a few hundred residents.

Is this the same St. Louis County as Duluth, Minnesota?
No. St. Louis County, Minnesota, home to Duluth, is a separate county more than 500 miles north.

More counties in this state: Towns and villages in Missouri.