Population and Build-Out

The Summit County Planning Department provides basic demographic information on the county’s population. Find information on

Related Resources

The following resources provide additional demographic information about Summit County, the State of Colorado and the nation as a whole:

Residential Build-Out
Residential Build-Out
A build-out analysis attempts to answer how much development has occurred in a community and how much development remains to be built. The Summary of Residential Build-Out in Summit County, Colorado (pdf) provides this information for Summit County, assuming continued growth subject to the zoning ordinances and subdivision regulations in place at the time of analysis.

Analysis Components

The build-out analysis is broken out by planning basin, and includes build-out numbers for both the unincorporated areas and incorporated towns in Summit County. (View a locator map (pdf) depicting the four planning basins and six incorporated towns within the county.) 
Build-out for the unincorporated portions of the county, and the Towns of Blue River and Montezuma has been calculated by the Summit County Planning Department. Build-out for the remaining four towns in the county (Breckenridge, Dillon, Frisco, and Silverthorne) was obtained from the respective town planning departments. 
The Summit County Planning Department works to update build-out numbers for the planning basins, and adds newly constructed residential units semi-annually (using certificates of occupancy issued by the County Building Department). Build-out numbers are reviewed by basin, subdivision and parcel. 
The residential build-out analysis is broken out into two categories: absolute build-out and realistic build-out.

Absolute Build-Out

Absolute build-out represents an evaluation of the existing zoning on every parcel of private land in unincorporated portions of the county and determines the maximum potential residential development allowed by that zoning. By subtracting the number of existing units built, we determine an approximation of what remains to be built. This is referred to as absolute build-out, because it represents the absolute or ultimate build-out potential that is permitted by existing zoning. 
 Absolute build-out is not necessarily a fixed or static number. Some factors that could potentially act to increase absolute build-out in the county include future land trades with the U.S. Forest Service; potential annexations and upzonings by towns of lands that are currently unincorporated; and the creation of new density for future affordable or workforce housing developments. 
Policies in the Countywide Comprehensive Plan for Summit County, Colorado limit or cap the creation of new density on unincorporated lands as a means of controlling absolute build-out. The County entered into an agreement with the Town of Breckenridge requiring the use of transferable development rights (TDRs) when upzoning within Town limits. The County continues to work with the towns of Blue River, Silverthorne, Dillon and Frisco to establish joint planning agreements addressing coordinated land use planning, density and transferable development rights (TDRs). 

Realistic Build-Out

Realistic build-out represents a more likely picture of the build-out that may occur in Summit County. It is unlikely absolute build-out, as described above, will be realized or achieved (i.e., the total number of units allowed per zoning will not likely be built). Realistic build-out factors in constraints that could preclude realization of the full development potential allowed under the existing zoning regulations. The factors that need to be considered and contribute to this assumption include, but are not limited to the following: 
  • On-site and off-site constraints to remaining development (e.g., backcountry parcels that are not readily accessible, parcels that are constrained by wetlands and steep slopes or lack water rights) 
  • Private property owners electing not to develop their property to its full potential or electing to keep large tracts of land intact because of a desire to maintain a large undisturbed land area
  • Development of some properties may be restricted by conservation easements in the future (existing conservation easements have been deducted from the current numbers in the attached analysis)
  • Private properties acquired for open space preservation (e.g., open space tax dollars or voter approved funding mechanisms to purchase properties to protect open space). 
Summary of Summit County Residential Build-Out
As shown in the build-out analysis, overall, as of December 31, 2022, approximately 32,892 units of the 43,009 units allowed per zoning have been built in the county. This represents an absolute residential build-out of 76% (including both the unincorporated areas and the incorporated towns). Summit County Planning Staff estimates that the realistic build-out for the county is approximately 39,454 units, which means that realistic build-out is approximately 83% (including both the unincorporated areas and the incorporated towns).

Observations and Additional Information
A number of observations can be made from the residential build-out analysis.

The data indicate that the incorporated towns are more built-out than the unincorporated portions of the county. Among the incorporated towns, the Town of Frisco is the most built-out at approximately 97%, followed by the towns of Breckenridge and Silverthorne. When looking at the respective planning basins (including both unincorporated areas and incorporated towns), in the context of absolute build-out, the Tenmile Basin is the most build-out of the four basins, with an absolute build-out of approximately 88%, followed by the Upper Blue and Lower Blue Basins. In terms of realistic build-out, all basins are roughly 83% built-out. 

The data also show that there are significantly more residential units built in the Upper Blue Basin than any other basin (including both unincorporated areas and incorporated towns). There are approximately 12,624 units built in the Upper Blue Basin, which is approximately twice the number of units built in the Lower Blue or Tenmile basins.   

For more information on the Summit County build-out analysis contact the Summit County Planning Department at 970-668-4200. 
Permanent Resident Population
Permanent Resident Population
The following table provides an overview of the distribution of the permanent resident population in Summit County. These population numbers are based on U.S. Census data and annual population estimates prepared by the State Demography Office in the Colorado Division of Local Government.

Summit County Permanent Resident Population

Area 1970 1980 1990 2000 2010 20201

Incorporated Areas

Breckenridge 548 818 1,285 2,408 4,540 5,078
Blue River 8 230 440 685 849 877
Dillon 182 337 553 802 904 1,064
Frisco 471 1,221 1,601 2,443 2,683 2,913
Montezuma N/A N/A 60 42 65 74
Silverthorne 400 989 1,768 3,196 3,887 4,402
Subtotal 1,609 3,595 5,707 9,576   12,928

Unincorporated Areas

Subtotal 1,056 5,253 7,174 13,972 15,066 16,647
Summit County Total 2,665






The 1970 - 2020 population numbers are based on U.S. Census data.

(View a locator map (PDF), depicting the four planning basins and six incorporated towns within Summit County.)
Approximately 53% of the permanent residents in the county live in unincorporated areas (properties located outside of town boundaries). The County's Snake River Basin has become the most populated of the unincorporated areas, primarily due to the increased permanent resident population in the Summit Cove and Dillon Valley neighborhoods (currently the two largest and most densely populated neighborhoods in unincorporated Summit County). Among the incorporated towns, the permanent resident population of Dillon increased most dramatically from 2010 – 2020; however, Breckenridge’s permanent resident population has increased the most significantly since 2010.
The 2020 Census data released by the State Demographer indicates that the permanent resident population of Summit County is 31,055. This represents an 11% increase in permanent residents from the 2010 Census. The State Demography Office estimates population in arrears as of July 1 of each year (e.g., the 2021 population estimate will be released by the State Demographer in July of 2022).