Blog · September 24, 2026 · Colorado
Boulder County, Colorado GIS Parcel Map Guide
Boulder, Longmont, Louisville, Lafayette, Superior, Lyons, Nederland, Jamestown and the foothills in between are all covered by the Boulder County Assessor’s free Property Search map.
Main page: Boulder County, CO GIS & Parcel Viewer (official map link, Boulder County facts and neighboring maps).
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Boulder County runs from the plains to the Continental Divide. The Assessor’s Property Search map packs sales, taxes, septic, floodplain and survey records into expandable panels beside the map.
Property Search, section by section
The Assessor’s map lets you search by address, owner name, street, subdivision, account, parcel number or section-township-range, or simply click a property. Results open as expandable sections:
- Basic Property Info and Assessment, with value changes and building attributes.
- Taxes, estimated by taxing authority.
- Sales History and Comparable Sales.
- Oblique Imagery for angled views of buildings.
- Zoning & Septic, Floodplain, Public Lands and election districts.
- Surveys, linking recorded surveys near the parcel.
Tools for selecting by graphic, buffering, coordinate search, mailing labels and printing all reports sit alongside. A Status button reports outages. Bookmark it via the Boulder row of our Colorado list, or pick the county on our county map.
How to find property lines in Boulder County
- Open the parcel and read the legal description in Basic Property Info.
- Check the Surveys section for recorded surveys that touch the lot.
- Order the deed and plat from the Clerk and Recorder.
- Hire a Colorado professional land surveyor to stake lines before building or fencing.
Mountain parcels may include old mining claims; our ALTA survey explainer covers the detailed surveys lenders sometimes require.
The Marshall Fire
On December 30, 2021, wind-driven flames swept through Louisville, Superior and unincorporated areas, destroying about a thousand homes. Rebuilding has reshaped whole neighborhoods, and energy and fire-resistance standards changed. The parcel map shows rebuilt homes with new assessments. Wildfire risk also affects insurance throughout the foothills.
The 2013 flood
In September 2013, days of rain sent floods down Boulder Creek, Left Hand Creek and the St. Vrain, hitting Lyons and Jamestown especially hard. Floodplain maps were revised afterward. The Floodplain section shows current risk. Buyers should also ask about past damage and any buyouts.
Open space and the Blue Line
Boulder and the county have bought tens of thousands of acres of open space, forming a greenbelt. The City of Boulder’s Blue Line limits water service above a set elevation on the mountain backdrop. Together these limit where new homes can go and help explain Boulder’s high land prices.
Septic and mountain building
Mountain homes typically rely on wells and septic. The Zoning & Septic section can show permits on file. County land use rules for site plans, building size and visual impact apply in the unincorporated mountains.
Two-year reappraisal
Colorado reappraises property every two years, with notices in odd years. The Assessment section shows value history; the Comparable Sales list helps with appeals.
Longmont and the eastern towns
Longmont, nearly as big as Boulder, sits along St. Vrain Creek on the plains. Erie straddles the Weld County line, and Superior stretches into Jefferson County, so some addresses need a second county’s records. Broomfield, once partly in Boulder County, became its own county in 2001. City zoning governs inside these towns, and each has its own permit office.
Nederland, Ward and old mining claims
West of Boulder, canyon roads climb to Nederland, Ward, Gold Hill and Jamestown. Nineteenth-century mining left patented claims with odd, overlapping shapes, and some old lots lack clear access. The 2010 Fourmile Canyon Fire burned many homes in this area. Rural addressing and road access are both worth checking on the map.
Mailing labels and buffers
Some land use applications require notifying nearby owners. The buffer and mailing label tools can build that list, though planning staff decide the official radius. The Public Lands section also flags nearby open space and national forest, such as Roosevelt National Forest and the Indian Peaks Wilderness.
Ag land, ditches and water rights
East of the foothills, farms around Longmont, Niwot and Hygiene rely on irrigation ditches whose water rights are often sold separately from land. A farm without ditch shares may be only dry pasture. Ask for the water rights history and share certificates, and note that the parcel map shows ditches but not who owns the water.
Accessory dwellings and small lots
The City of Boulder and several towns now allow accessory dwelling units under set rules. Lot size, parking and owner occupancy requirements vary. Look at lot dimensions on the map and then check the city code.
When the map is down
The Assessor’s Status button reports planned maintenance and known outages, which saves guessing whether the problem is your browser. If an address looks wrong on the map, the app’s Incorrect Address link sends the report to county staff, who manage addressing separately from assessments. Account numbers and parcel numbers are different identifiers here, so keep both when calling the office.
Is the Boulder County GIS map accurate?
The Assessor’s parcel lines are for assessment. The Surveys section is a helpful bridge to recorded surveys, but a new survey controls. See what GIS lot lines mean.
Other Colorado guides
For Fort Collins, see our Larimer County guide. Browse the rest of the state on the Colorado hub.
Frequently asked questions
Can I find recorded surveys on the Boulder County map?
Yes. The Property Search app has a Surveys section linking surveys near the parcel.
Does the Boulder County map show septic information?
A Zoning and Septic section can show permits on file for the parcel.
What is the Blue Line in Boulder?
A city limit on water service above a set elevation along the mountain backdrop.
How often does Boulder County reappraise?
Every two years, with notices mailed in odd-numbered years.
Open the official Boulder County GIS viewer Boulder County in the Platbookmapper directory
Not a survey. County GIS and tax parcel maps are assessment and planning layers. They are not a substitute for a recorded plat, deed, or licensed survey — especially for fences, setbacks, or boundary disputes.