St. Charles County vs St. Louis County
Two neighbouring counties in Missouri, compared on population, size, income and housing. They share 48 mi of border.
St. Charles County
Missouri
St. Louis County
Missouri
Both outlines are drawn at true relative size. St. Charles County spans about 73.2 km at its widest.
Side by side
| Measure | St. Charles County | Difference | St. Louis County |
|---|---|---|---|
| Population | 426,499 | -57.0% | 990,911 |
| Change since 2020 | 4.9% | +6.1 pp | -1.2% |
| Land area | 560.3 sq mi | +10.2% | 508.5 sq mi |
| Population density | 761 per sq mi | -61.0% | 1,949 per sq mi |
| Median household income | $104,692 | +26.2% | $82,936 |
| Median home value | $320,800 | +15.9% | $276,800 |
| Median age | 39.8 | -1.2% | 40.3 |
| Households | 161,311 | -61.0% | 413,849 |
| Housing units | 167,163 | -62.5% | 446,192 |
Sources: US Census Bureau, Population Estimates Program, Vintage 2025 Population Estimates, released 26 March 2026; US Census Bureau, Gazetteer Files, 2025 Gazetteer Files, released 10 September 2025; US Census Bureau, American Community Survey, American Community Survey 2020-2024 5-Year Estimates, released 29 January 2026; US Census Bureau, County Adjacency File, 2025 County Adjacency File, released 15 September 2025. The difference column is computed here: the first county's figure against the second, expressed as a percentage of the second. The change-since-2020 row is the exception: two growth rates differ in percentage points (pp), not percent. Retrieved 30 August 2026.
What the numbers say
- St. Louis County holds about 2.3 times the population of St. Charles County: 990,911 against 426,499.
- St. Charles County covers more ground, at 560.3 square miles against 508.5.
- St. Louis County is the more crowded of the two, at 1,949 people per square mile against 761.
- Median household income is higher in St. Charles County, by 21,756 dollars a year.
- Since 2020, St. Charles County has grown by 4.9% and St. Louis County has shrunk by 1.2%.
- They share 48 mi of common border, which the Census Bureau publishes in its county adjacency file and which almost no other county reference presents.
Full pages
Want a different pair? Compare any two of the 3,144 US counties.
Rebuilt from source data 30 August 2026. How these figures are produced.