Colorado

Buying Land in Arapahoe County, Colorado

Arapahoe County is Aurora, Centennial, and most of the rest of the southeast Denver metro -- one of Colorado's most populous counties, on track to become the metro's largest within a few years. Its raw-land market survives in a narrow band of eastern plains around Byers and Deer Trail, under the county's own Land Development Code and, as of 2026, its own newly updated septic rules.

Rural Land Market: Real but Confined to the Eastern Plains

Case-by-case / verify locally

Arapahoe County had roughly 674,000 residents as of 2025 -- the third-most-populous county in Colorado -- concentrated almost entirely in Aurora, Centennial, Englewood, Littleton, and the other incorporated cities that make up the southeast Denver metro. The county's agricultural and rural-residential land sits on the eastern plains, around the towns of Byers and Deer Trail and the unincorporated community of Watkins, along the I-70 corridor roughly 40-55 miles east of Denver. Treat a land search here as targeting that specific eastern band, not the county generally.

County's Own Land Development Code: Agricultural and Rural Residential Districts

Generally favorable

Unincorporated Arapahoe County is governed by its own Land Development Code, administered by the Planning and Land Development Division. The code's Agricultural Estate (A-E) and Agricultural-1 (A-1) districts, and its Rural Residential districts (RR-A, RR-B, RR-C), are written specifically to preserve a rural, agricultural economic base and lifestyle in the eastern part of the unincorporated county. RR-A carries a confirmed 9-acre minimum lot size; confirm RR-B and RR-C minimums and the A-E/A-1 thresholds directly with the county rather than assuming a figure.

Septic Under a New 2026 County Regulation

Could not confirm

Arapahoe County left the multi-county Tri-County Health Department (it was the last of the three member counties, staying through 2022) and now runs its own Arapahoe County Public Health department, which adopted a new On-Site Wastewater Treatment System (OWTS) Regulation effective May 7, 2026. Because this is a recent rule change, confirm you're working from the current 2026 regulation -- not an older Tri-County-era standard -- for any septic feasibility question.

Growth Trajectory

Could not confirm

Arapahoe County is projected to become the most populous county in the Denver metro area by around 2030, surpassing the City and County of Denver. That growth pressure is concentrated in the incorporated cities, not the eastern plains rural land, but it is worth factoring into any longer-horizon view of how close development might eventually reach a specific eastern-county parcel.

A populous metro county with a real, narrow rural-land niche on the eastern plains

Arapahoe County runs from the dense southeast Denver suburbs -- Aurora (the county's largest city, with over 341,000 residents), Centennial, Englewood, Littleton (the county seat), Cherry Hills Village, and Greenwood Village -- out across roughly 805 square miles to the Colorado eastern plains. The overwhelming majority of the county's population and built land is in that western, incorporated portion, each city carrying its own separate zoning code, not the county's. The county's real rural-land market is on the other end: the towns of Byers and Deer Trail, and the unincorporated community of Watkins, sit along and near the I-70 corridor in the county's eastern reaches, in a landscape the county's own code describes as part of a native-prairie, agricultural-corridor region shared with neighboring Adams County to the north.

If you're evaluating Arapahoe County for acreage, agricultural land, or a rural homesite, expect the search to functionally mean "the area around Byers and Deer Trail," not the county as a whole -- and expect land character there (open plains, working farms and ranches, low population density) to look nothing like the suburban half of the county 40 to 55 miles to the west.

The county's own Land Development Code: agricultural and rural-residential zoning for the eastern plains

Unincorporated Arapahoe County -- meaning land outside Aurora, Centennial, and the county's other municipalities -- is governed by its own Land Development Code, which bundles together zoning and subdivision regulations and implements the county's Comprehensive Plan. The code's agricultural zone districts, Agricultural Estate (A-E) and Agricultural-1 (A-1), are explicitly written to promote and preserve a rural, agricultural economic base and lifestyle in the eastern parts of the unincorporated county, with residential uses treated as secondary to that agricultural character. Separately, three Rural Residential districts -- RR-A, RR-B, and RR-C -- are meant to allow low-density rural-residential development and small-scale agriculture while still protecting the area's rural character; RR-A carries a confirmed minimum lot size of 9 acres, though the specific thresholds for RR-B and RR-C should be confirmed directly with the county rather than assumed.

The Planning and Land Development Division, part of the county's Public Works and Development Department, administers the code and reviews land-development applications; the separate Zoning Division handles day-to-day zoning questions and permits. Because the Land Development Code has been actively updated in recent years (a March 2026 revision is the current version as of this review), confirm you're referencing the current text and the actual zoning designation on a specific parcel before assuming a particular district's rules apply.

A new county health department, and a 2026 septic regulation to match

Arapahoe County's septic oversight has changed hands recently. The county was a founding member of the multi-county Tri-County Health Department (shared historically with Adams and Douglas counties) and was the last of the three to remain after Adams and Douglas withdrew; Tri-County Health Department dissolved entirely at the end of 2022, and Arapahoe County stood up its own Arapahoe County Public Health department. That new department has since adopted its own On-Site Wastewater Treatment System (OWTS) Regulation, effective May 7, 2026, including a new licensing requirement for OWTS designers, installers, and inspectors.

For any parcel on the eastern plains relying on a septic system, confirm current requirements directly with Arapahoe County Public Health rather than relying on older Tri-County-era guidance.

Who to Call Before Buying Land in Arapahoe County

A direct phone number and email for Arapahoe County Public Health's Environmental Health/septic division could not be independently verified as of this review and are left blank rather than guessed -- confirm current contact details on the county's own site. The Land Development Code also references separate '1041 Regulations' (Colorado's areas-and-activities-of-state-interest authority) for certain large-scale developments; this page does not cover 1041 review in depth, since it applies to specific project types rather than ordinary land purchases.

Planning & Zoning

Arapahoe County Public Works and Development Department -- Planning and Land Development Division

Confirming a parcel's zoning district under the Land Development Code, permitted uses in the A-E/A-1 agricultural and RR-A/RR-B/RR-C rural-residential districts, and subdivision or land-development applications.

Phone: (720) 874-6650Email: zoning@arapahoegov.comOfficial website →

Septic / Onsite Wastewater