Area Code 636

Missouri

Area code 636 serves Missouri, primarily O'Fallon, in the Central Time (CT) time zone. It was created from a split of area code 314.

Split Area Code

This area code was created by splitting an existing area code into separate geographic regions. When a split occurs, some customers in the original area code region are assigned the new area code.

This area code was split from area code 314 (St. Louis).

In service since: 22-May-1999

Learn more about overlay and split area codes →

Demographics & Economics

Total Population: 1,330,725
Population Density: 222 people/sq mi
above U.S. average (U.S.: 93 people/sq mi)
Median Household Income: $81,340
near U.S. median (U.S.: $75,144)
Poverty Rate: 8.2%
below U.S. average (U.S.: 11.5%)
Unemployment Rate: 3.6%
near U.S. average (U.S.: 3.6%)
Education Attainment: Bachelor's Degree+
33.2%
near U.S. average (U.S.: 33.7%)
High School or Lower
30.2%

Statistics are population-weighted aggregations from Census ACS 5-year estimates. Population figures are approximate — see Sources & Methodology for details on how area code populations are derived.

See how this area code compares to all US area codes in the Statistics dashboard.

Time Zone

Central Time (CT)

NANPA Relief Status

According to the latest NANPA analysis (July 2026), this area code is not currently listed as exhausting within the next 36 months. No relief planning is in progress for this NPA.

Source: NANPA NPA Relief Planning Reports · See all relief planning statuses

Current Time

Central Time (CT)

Prefix Utilization

Geographic Coverage

State

Major Cities

O'Fallon
St. Charles
St. Peters
Chesterfield
Wentzville
Wildwood
Ballwin
Hazelwood
Arnold
Manchester
Lake St. Louis
Washington
Troy
Dardenne Prairie
Festus
Union
Eureka
Town and Country
Ellisville
Sunset Hills
Warrenton
Murphy
Pacific
Valley Park

and 62 more cities

Area Code 636 geographic coverage map (light mode)

Demographics

The estimated population served by area code 636 is approximately 1,330,725. The population density is 222 people per square mile, which is higher than the national average of 93. The median household income is $81,340, which is near the national median of $75,144. Approximately 33.2% of adults hold a bachelor's degree or higher, compared to the national rate of 33.7%. This rate is near the national average. The poverty rate stands at 8.2%, which is lower than the national rate of 11.5%.

History

Area code 636 was created from a split of area code 314. It was introduced in 1999 as part of a geographic division to provide additional numbering resources.

County Coverage

Population-weighted county share based on aggregated ZCTA population (100% = total mapped population for area code 636).

County	Population	Share
St. Charles, MO	418,481	31.4%
Jefferson, MO	283,401	21.3%
St. Louis, MO	275,695	20.7%
Franklin, MO	106,743	8.0%
Lincoln, MO	89,263	6.7%
St. Francois, MO	52,729	4.0%
Warren, MO	48,820	3.7%
Ste. Genevieve, MO	27,913	2.1%
Washington, MO	24,869	1.9%
Montgomery, MO	2,811	0.2%