Published
3,606 people and nearly flat: what St. Anthony’s census numbers actually say
How big, and which way it is heading
Every other chapter of the city’s comprehensive plan quietly leans on one question: how many people, and which direction next. The plan’s population chapter answers it with three plain counts:
“The 2020 United States Decennial Census estimated the population at 3,606 while the 2010 census listed the population at 3,542, with 3,342 people residing in the city in 2000. The most recent figure accounts for 27% of the 13,388 people who called Fremont County home in 2020.”
— City of St. Anthony Comprehensive Plan, ch. 2, Population (2023). Retrieved 28 September 2026
St. Anthony is the county seat and largest population center for Fremont County — a little over a quarter of everyone in the county lives here. The trend line behind those counts is nearly flat: a 6.5% increase between 2000 and 2010, then a 1.8% increase from 2010 to 2020. The plan’s history graph starts in 1970, and it shows the only dip of the half-century: “a reduction in population between 1980 and 1990 with gradual growth from 1990 forward.”
Fifty years in four sentences
The chapter’s longer arc, as the plan states it:
- The 1970s: the city’s population grew 11%.
- The 1980s: it declined 6%.
- The 1990s: it increased 11% again.
- 1970–2004 overall: about 19%, or 525 people, roughly 0.6% per year.
That is the shape of a town that grows steadily rather than in booms — the fact a builder should plan inventory around. And the map has grown faster than the headcount lately: “St. Anthony has also grown in area since the 2012 comprehensive plan’s adoption as additional property has been annexed into the city.” The annexation machinery moves the line; the census counts who is inside it.
Households, units, and the vacancy number
The housing-side counts matter more to a builder than the headline population:
- 1,156 households and 888 families (2020 census)
- residing in the city’s 1,300 available housing units
- of which 90, about 11%, were vacant
- population density around 2,300 people per square mile — against 7.2 per square mile for Fremont County as a whole
The plan sources the household figures the way it received them: US Census Bureau, DP-02, Selected Social Characteristics in the United States: 2020 S1101 (ACS 5-Year Estimates Data Profiles). City density versus county density is the whole story of the valley in two numbers — one compact town seat surrounded by open ground.
The plan doubts its own census
Unusually for an official document, the chapter argues with its own numbers. Many vacant lots in the city have been built out in the last decade, and other housing projects have been constructed and are currently occupied — so “it is questionable whether the census numbers accurately reflect all population changes in the last few years.” Projects contemplated by developers or under review could push growth past what the 2010–2020 estimates captured.
The second squeeze is short-term rentals: with internet-based services such as AirBNB and VRBO facilitating rentals shorter than 30 days, some units have been “effectively removed … from long term rental or owner occupied use.” A builder reading the 90-unit vacancy figure should read it with that leak in mind.
Scenarios for the next decade
The plan converts its history into three growth scenarios, each with a housing bill:
- 2% growth: only 72 new residents, requiring around 24 housing units.
- 6% growth: 216 new residents, requiring housing for 72 new households.
- 11% growth (the highest rate of the last 50 years): 396 additional residents, requiring about 132 units, either vacant or new construction.
What drives the upside, per the plan: proximity to Rexburg and BYU-Idaho to the south, growth pressure from the Jackson Hole and Teton Valley region, and continued growth around Island Park and northern Fremont County.
Reading the numbers before you build
- Plan capacity against the flat baseline, not the boom scenario — the last measured decade was 1.8%, and the plan itself doubts the census undercounts recent building.
- Treat the 90 vacant units as a soft number: the plan’s own short-term-rental observation says some of that stock never reaches a long-term buyer or tenant.
- Check whether growth near you comes as people or as land — annexations since the 2012 plan have grown the map faster than the population.
- Match the scenarios to what services the lot can reach and where the hazards chapter draws its lines before committing to a schedule.
- Then pressure-test the whole picture — counts, lots, and timing: (208) 656-1745.
The census chapter is the denominator under everything else this plan does: which belt of jurisdiction a parcel sits in, how the street grid carries the town, and how much service capacity the city has to budget for the next decade of rooftops.
Common questions
What is the population of St. Anthony, Idaho?
The 2020 United States Decennial Census put the population at 3,606. The 2010 census listed 3,542, and 3,342 people resided in the city in 2000. The 2020 figure accounts for 27% of the 13,388 people who called Fremont County home that year.
Is St. Anthony growing?
Slowly. The comprehensive plan reports a 6.5% increase between 2000 and 2010 and a 1.8% increase from 2010 to 2020. The longer graph starting in 1970 shows one decline, between 1980 and 1990, with gradual growth from 1990 forward.
How many households are in St. Anthony?
As of the 2020 census, 1,156 households and 888 families resided in the city's 1,300 available housing units, of which 90, about 11%, were vacant. The plan cites these from US Census Bureau DP-02, Selected Social Characteristics in the United States: 2020 S1101.
What is the population density of St. Anthony?
Around 2,300 people per square mile based on the 2020 census, against a Fremont County density of 7.2 per square mile. The contrast captures the region's shape: one compact county-seat town surrounded by largely open valley floor.
What growth does the comprehensive plan project?
Three scenarios for the next decade: a 2% growth rate would mean only 72 new residents, 6% would mean 216, and 11% - the highest rate of the last 50 years - would add 396. The housing requirement ranges from around 24 units at the low end to about 132 at the high end.
Why does the plan question its own census numbers?
Many vacant lots have been built out in the last decade and other housing projects are constructed and occupied, so the plan says it is questionable whether the census numbers reflect all recent population changes. Projects under review could accelerate growth past the 2010-2020 estimates.
What does the plan say drives growth in St. Anthony?
Proximity to Rexburg and BYU-Idaho in Madison County to the south is called perhaps the greatest impact, followed by growth pressure from the Jackson Hole and Teton Valley region and continued growth around Island Park and northern and eastern Fremont County.
Has St. Anthony grown in land area?
Yes. The plan notes the city has grown in area since the 2012 comprehensive plan's adoption as additional property has been annexed into the city, and that many people live within the city's area of impact even where the line has not moved.
What do the vacancy numbers mean for builders?
The census estimated around 90 vacant units, but the plan observes that short-term rentals through services like AirBNB and VRBO have removed some units from long-term rental or owner-occupied use. Builders should treat the vacancy figure as softer than it looks.