Buying in Unincorporated Colorado: Douglas, Jeffco and More

An unincorporated community in Colorado is a place with a name and a mailing address but no city government: the county commissioners are its council, the county building division issues its permits, and the county road and bridge department plows its roads. Highlands Ranch, Ken-Caryl Ranch, Evergreen, Conifer, Roxborough Park, Franktown, Strasburg and most of Elbert and Weld counties all work this way.

Buying in unincorporated Douglas, Jefferson, Arapahoe, Adams, Weld or Elbert County changes who you pay, who you call and what you are allowed to build. This guide answers the questions Front Range buyers ask before they write an offer on a home outside city limits.

How unincorporated Colorado came to be

Colorado's counties came first. The territorial legislature drew 17 counties in 1861, and towns incorporated inside them one by one as mining camps and railroad stops grew. Everything outside a town's boundary stayed under the county, and Colorado law still lets any area stay that way forever. The national definition in What is an unincorporated community is the same one Colorado uses: a named place with no municipal corporation of its own. Colorado has 64 counties and about 270 municipalities; the land between the municipalities is unincorporated.

Two forces shaped the modern map. Cities annex land at their edges under Title 31 of the Colorado Revised Statutes, so a home in unincorporated Arapahoe County one year is inside Centennial the next. And large master-planned communities were built on county land on purpose: Highlands Ranch started in 1981 in unincorporated Douglas County with a metropolitan district and the Highlands Ranch Community Association instead of a city hall, and it still has more than 100,000 residents and no mayor. Centennial incorporated in 2001 and Castle Pines in 2008, both carved from unincorporated county land by residents who voted to form a city.

How do I tell if a home is inside city limits?

The mailing address does not tell you. The post office assigns city names by delivery route, so a "Littleton" address sits in unincorporated Jefferson County (Ken-Caryl, Columbine), unincorporated Arapahoe County (Columbine Knolls, the area south of Bowles Avenue), or the City of Littleton itself. "Parker" addresses cover unincorporated Douglas County east of the town. "Aurora" addresses reach into unincorporated Arapahoe and Adams counties near Watkins.

• Look at the county assessor's record: the tax-area or tax-district code lists every taxing authority. No city listed means unincorporated.
• Look at the title commitment: the legal description names the county, and the exceptions list metro districts and HOAs.
• Look at the tax bill: a city line item (for example "City of Aurora") means incorporated; a "Road and Bridge" county line plus a fire protection district and no city means unincorporated.

What county services replace city services?

Do I pay less tax in unincorporated Colorado?

Sales tax, yes. Property tax depends on the districts, not on the city line.

Sales tax. A city sales tax of 3% to 4% disappears outside city limits. Colorado's state rate is 2.9%. Add the county rate and, inside the RTD boundary, 1.0% for RTD and 0.1% for the Scientific and Cultural Facilities District. Unincorporated Jefferson County lands at 4.5%, unincorporated Arapahoe County at 4.25%, unincorporated Adams County at 4.75%, and Highlands Ranch at 5.0%. Unincorporated Weld County outside RTD pays the state 2.9% and nothing else. Compare that with 7.9% in Castle Rock or 8.81% in Denver. On a $60,000 truck the difference is $1,500 to $3,000. Confirm any address with the Colorado Department of Revenue's sales tax lookup, because special districts move the number.

Property tax. Your bill is the county assessed value times the sum of every mill levy on the parcel: county, fire district, water and sanitation district, library district, metro district and so on. A metro district in a newer unincorporated subdivision adds 30 to 60 mills to pay off the bonds that built the streets and water lines, which puts a $700,000 home in a new Douglas County metro district above a $700,000 home in an older part of Littleton. Read our Denver special district and metro district tax guide and the post on how HOAs, metro districts and taxes affect Denver suburb buyers before you compare two homes by price alone.

What is a metro district and why does it matter in unincorporated areas?

A metropolitan district is a special taxing district formed under Title 32 of the Colorado Revised Statutes. In a city, the city builds streets and water mains. In unincorporated county land, the developer forms a metro district, sells bonds, builds the infrastructure, and the homeowners repay the bonds through a mill levy for 20 to 40 years. The district also runs the parks, pool and landscaping in many subdivisions. Its budget, board and debt schedule are public records filed with the Colorado Department of Local Affairs; read them for any home in a district younger than 15 years.

Well and septic: what changes when there is no city utility

Outside a water and sanitation district, the home runs on a private well and an onsite wastewater treatment system (OWTS). Both are permitted by the state and the county, and both come with rules that decide what you build.

• Well permits come from the Colorado Division of Water Resources. A household-use-only well serves one home and no outdoor irrigation. A domestic exempt well is allowed only on parcels of 35 acres or more and serves up to three single-unit homes, one acre of irrigation and domestic animals. Ask for the well permit number and pull it before you write an offer; the permit, not the seller, says what the water is allowed to do.
• Septic permits come from the county health department under Colorado Regulation 43. Jefferson County and Boulder County require an OWTS inspection and use permit when title transfers. Douglas County Health Department, Arapahoe County Public Health and Adams County Health Department each publish their own transfer rule; read the current page before the inspection deadline in your contract.
• Costs: a well pump replacement runs $2,500 to $6,000 on the Front Range; a new conventional septic system runs $15,000 to $30,000, and an engineered system on clay or a high water table runs more.

Our Colorado horse property buying guide walks through well permits, septic sizing and access easements for acreage buyers.

What can I build on unincorporated land?

County zoning is looser on use and stricter on lot size than city zoning. Douglas County and Jefferson County both use an A-1 agricultural zone with a 35-acre minimum and residential rural zones with 2.5- to 10-acre minimums. Elbert and Weld counties allow agricultural buildings, horses and home businesses in their rural zones that a city would prohibit. Every county still requires a building permit for a house, a detached garage, a barn over a size threshold, a deck and a finished basement.

• Accessory dwelling units: Colorado's 2024 ADU law applies to cities inside metropolitan planning areas, not to unincorporated counties. Douglas County has its own ADU rules; read our Douglas County ADU regulations guide.
• Outbuildings: read does that big shop add value to a Colorado acreage property before you build one.
• Surveys: acreage lots have fence lines that wander; our Colorado ILC vs. land survey guide explains which document to order.

Which Front Range unincorporated areas do buyers ask about?

• Douglas County: Highlands Ranch, Roxborough Park, Franktown, the Castle Pines Village side of Castle Pines, and acreage between Parker and Elizabeth. Search homes in Highlands Ranch and read the Highlands Ranch HRCA, rec center and water guide.
• Jefferson County: Ken-Caryl Ranch, Evergreen, Conifer, Indian Hills and the Columbine area with Littleton addresses. Search homes near Morrison for the foothills side.
• Arapahoe County: the Columbine Valley edge, Byers and Strasburg on the eastern plains.
• Adams County: Henderson, Watkins and acreage north of Brighton. Search homes near Brighton.
• Weld County: acreage around Greeley, Windsor and Johnstown with no county sales tax. Search homes in Greeley.
• Elbert County: everything outside the towns of Elizabeth, Kiowa and Simla, most of it on 35-acre or larger parcels with wells.

What to verify before you buy outside city limits

1. Pull the assessor's tax-area code and list every district on the parcel.
2. Get the metro district's most recent budget and bond balance from the Department of Local Affairs filings.
3. Pull the well permit from the Division of Water Resources and the septic permit from the county health department.
4. Ask the county road and bridge department whether the road to the house is county-maintained or private.
5. Get a written quote from a trash hauler and confirm which fire protection district covers the address.
6. Read the county zoning resolution for the parcel's zone district before planning a shop, ADU or horses.

Where to go next

• Search every home for sale in Colorado, in and outside city limits
• Colorado horse properties and acreage for sale
• How a Colorado property tax bill works
• Arapahoe County property taxes by city
• Equestrian and acreage homes near Denver, Parker and Evergreen
• Meet the Kenna Real Estate Group agents

Talk to the Kenna Real Estate Group

We sell homes in unincorporated Douglas, Jefferson, Arapahoe, Adams, Weld and Elbert counties every month, and we pull the district, well and septic records before you write the offer. Call or text 303-955-4220. A live person answers. Not a robot, not a phone tree. You can also search every home for sale in Colorado and filter by county.