ST. LOUIS COUNTY, Mo. – St. Louis County accounts for nearly one-third of the Greater St. Louis Metropolitan Area’s population.
Around 1 million people call St. Louis County home in the present day, according to U.S. Census figures. It hasn’t changed too much in size in recent history, but a recent FOX 2 analysis revealed that St. Louis County gained around 50,000 residents in a 50-year span between 1970 and 2020.
There are nearly 100 municipalities in St. Louis County. In the 21st century, very few have seen dramatic changes in population, but some have noticed steady growth.
Where has St. Louis County grown most over the past decade? Population gains are a bit scattered, but they’re generally common among the county’s highest-populated suburbs, particularly those home to at least 10,000 people.
Based on Census figures, from 2010 to 2020, the city of Chesterfield led all county municipalities in total population growth. It added more than 2,500 people, increasing around 5% in size over the course of a decade.
In terms of percentage growth, during that same timeframe, the city of Eureka grew the fastest among county municipalities. It grew nearly 15% in population from 2010 to 2020, adding around 1,500 new residents.
Depending on classification, one could argue the city of Twin Oaks in west St. Louis County grew the fastest among all St. Louis County suburbs. It increased at nearly a 50% clip in population from 2010 to 2020, but it was also previously not deemed a municipality until 2016.
Following Chesterfield, these were the next three largest population gains in St. Louis County among suburbs with at least 1,000 residents from the start of the last decade to this one:
| 2010 population | 2020 population | Total gain | |
| Kirkwood | 27,540 | 29,461 | +1,921 |
| Eureka | 10,189 | 11,646 | +1,457 |
| Clayton | 15,939 | 17,355 | +1,416 |
Following Eureka, these were the next three largest population percentage increases in St. Louis County among suburbs with at least 1,000 residents from the start of the last decade to this one:
| 2010 population | 2020 population | Percent gain | |
| Olivette | 7,737 | 8,504 | +9.9% |
| Des Peres | 8,373 | 9,193 | +9.8% |
| Ellisville | 9,133 | 9,985 | +9.3% |
As for the St. Louis region, St. Louis County is sandwiched in between two boundaries with contrasting population trends. The City has lost around half of its population over the last half-century, while St. Charles County has nearly tripled in size, per Census figures. FOX 2 recently explored the growth of many St. Charles County municipalities following last month’s population analysis.
Some state-based projections hint that St. Louis County’s population might decrease slightly amid those trends, but the county is currently home to around 40,000 people, above the state’s original 2030 population projection.
