Permits through August 2026Yearly permits since 1995St. Clair County index 1977–2025
St. Clair County (100 = first year)United States, rebased to the same startNBER recession
House prices are indexed by county, not by city: this is St. Clair County's FHFA index, with the national index rebased to the same start.
Census Bureau notes: building permit figures cover new privately owned housing units authorised by permit-issuing places; permits do not mean the units were started or completed, and places that report less often than monthly are imputed in monthly totals. FHFA notes: The FHFA HPI is a broad measure of the movement of single-family house prices. The FHFA HPI is a weighted, repeat-sales index, meaning that it measures average price changes in repeat sales or refinancings on the same properties.
In the 12 months to August 2026, building permits in O'Fallon, Illinois, covered 213 housing units (−11.2% year on year); the place lies in St. Clair County.
88 of those units were single-family houses (41%), 92 were in two- to four-unit buildings and 33 in buildings of five or more units. That is 6.5 units per 1,000 residents, well above the county's 1.7 and well above the state's 1.5.
Since 1995 the place has authorised 6,864 units, with the busiest year 2002 (488 units). St. Clair County's FHFA house price index rose +69.3% over the ten years to 2025.
213units permitted, 12 months to August 2026−11.2% on the previous 12 months
88single-family units41% of the total
33units in 5+ unit buildings15% of the total
6.5units per 1,000 residentsSt. Clair County 1.7 · Illinois 1.5
Permits by month and structure type
Housing units authorised in O'Fallon by month, latest 24 monthssingle-family2+ unit buildings
Units, 12 months to August 2026
O'Fallon
St. Clair County
Illinois
United States
All housing units
213
421
19,157
1,418,086
Single-family (1 unit)
88 (41%)
278 (66%)
10,712 (56%)
888,241 (63%)
2 units
92
94
502
34,814
3–4 units
0
0
871
17,298
5 or more units
33 (15%)
49 (12%)
7,072 (37%)
477,733 (34%)
Units per 1,000 residents
6.5
1.7
1.5
4.1
Change on previous 12 months
−11.2%
−30.4%
−5.7%
−0.1%
Permits by year since 1995
Housing units authorised in O'Fallon by year, 1995–2025single-family2+ unit buildings
6,864 units since 1995; the busiest year was 2002. Annual figures include units imputed for months a place did not report.
Home prices in St. Clair County
FHFA's index for St. Clair County rose +69.3% over the ten years to 2025 (+5.4% a year) and +5.3% in the latest year, against +64.6% and +5.7% for Illinois. Full county page: decade table, peak-to-low declines, every ZIP code and every permit-issuing place in the county.
Questions and answers
How many homes are being built in O'Fallon, IL?
213 housing units were authorised by building permits in the 12 months to August 2026, against 240 in the previous 12 months.
What kind of housing is being permitted in O'Fallon?
88 single-family units, 92 in two-unit buildings, 0 in three- and four-unit buildings and 33 in buildings of five or more units.
How does O'Fallon compare with its county and state?
6.5 units per 1,000 residents in O'Fallon, 1.7 in St. Clair County and 1.5 in Illinois.
How have home prices moved in St. Clair County?
FHFA's index for St. Clair County rose +69.3% over the ten years to 2025 and +5.3% in the latest year; the county page has the full series.
What does a permit count?
A housing unit authorised by a building permit for new privately owned residential construction, as reported to the Census Bureau Building Permits Survey by the permit-issuing office. Permits are not completions; some permitted units are never built, and places that report only annually are imputed in monthly figures.
Provenance
Permits: US Census Bureau, Building Permits Survey, place-level monthly and annual files through August 2026 (permit office 569800); county and state comparisons from the county and state files. Population: Census Bureau vintage 2025 estimates for incorporated places, matched on FIPS place code where the permit office is one. House price index: Federal Housing Finance Agency. Public domain. Corrections · Building Permits Survey.