Idaho local data guide

Projected Population Growth for the Treasure Valley

The Treasure Valley, primarily centered on Ada and Canyon Counties, continues to experience significant population expansion. As of April 2026, the estimated population for Ada and Canyon Counties stands at 876,760, with the broader four-county region—including Boise and Elmore Counties—totaling 915,940. Long-range planning models from the Community Planning Association of Southwest Idaho (COMPASS) project that the region is on a trajectory to exceed 1 million residents in the coming decades, with targets approaching 1.075 million by 2050 and 1.3 million by 2055.

Updated with grounded research as of 2026-09-19.

The short answer

The Treasure Valley is currently in a period of sustained growth. As of 2026, the combined population of Ada and Canyon Counties is 876,760, reflecting an increase of 150,000 residents since the 2020 Census. Regional planning agencies project this upward trend to continue, with forecasts suggesting the population will surpass 1 million in the coming decades, reaching approximately 1.075 million by 2050 and continuing toward 1.3 million by 2055 based on current long-range transportation planning targets.

Key facts

2026 Estimated Population (Ada & Canyon Counties)
876,760
2026 Estimated Population (4-County Total)
915,940
2050 Population Forecast (Ada & Canyon Counties)
1,075,000

Current Population Estimates (2026)

COMPASS (Community Planning Association of Southwest Idaho) publishes annual population estimates to assist in regional planning. These figures are derived from the most recent decennial Census data, supplemented by local building permit records, household size metrics, and annexation data. As of April 2026, the four-county region (Ada, Canyon, Boise, and Elmore) reached a population of 915,940, marking a 20% increase since the 2020 Census.

  • Ada and Canyon Counties: 876,760 residents.
  • Boise and Elmore Counties: 39,180 residents.
  • Growth is observed throughout the region, though smaller cities like Star and Kuna have seen distinct year-over-year percentage increases compared to larger municipalities.

Long-Range Forecasts

Population forecasts are essential components of the region's long-range transportation plans, such as 'Communities in Motion.' These models help officials anticipate infrastructure needs, housing requirements, and job growth.

  • 2050 Horizon: Forecasts anticipate approximately 1.075 million residents in Ada and Canyon Counties.
  • 2055 Outlook: The COMPASS Board has accepted a forecasted 2055 population of 1.3 million for Ada and Canyon Counties, which serves as a foundation for ongoing regional planning updates.

Methodology and Planning Context

Population figures are not static numbers; they are estimates based on economic, migration, and development trends. COMPASS employs different methodologies for urbanized areas (Ada and Canyon) versus more rural areas (Boise and Elmore) due to the variance in available data, such as high-frequency building permit reporting in metropolitan zones.

  • Planning Targets: Forecasts should be viewed as planning targets for infrastructure and services rather than guaranteed future counts.
  • Dynamic Adjustments: Models are frequently updated to reflect actual growth patterns, construction activity, and economic shifts.

Common questions

How does COMPASS calculate these population estimates?

COMPASS uses the most recent decennial Census as a baseline. For Ada and Canyon Counties, they integrate data from local building construction permits, current household sizes, vacancy rates, and recent city limit annexations.

Why do estimates for Boise and Elmore Counties differ from Ada and Canyon?

Because Boise and Elmore Counties are more rural, they lack the same high density of municipal data sources available in urban areas. As a result, COMPASS applies a slightly different methodological approach to calculate their populations.

Are these population forecasts fixed predictions?

No. These are demographic forecasts and planning targets used to guide long-range transportation and infrastructure investments. They are subject to change based on actual growth, economic conditions, and migration trends.

Related Idaho questions

  • What is the Communities in Motion 2050 plan?
  • How does population growth impact Treasure Valley infrastructure funding?
  • Where can I find historical population data for specific Treasure Valley cities?

Sources and verification