Jefferson County School District R-1

Where this district is the answer, and where it is not

The counts below come from the census blocks assigned to Jefferson County School District R-1, grouped by the ZIP Code area each block falls in. The Census Bureau publishes the blocks; the grouping is computed here, and it is the only place these particular numbers exist.

• Homes inside the boundary252,739
• Residents590,611
• ZIP Code areas it reaches34
• Where it is the only district15
• Where it shares with another district16
• Where it holds under half a percent3
• Land area768 square miles
• Homes per square mile329

The ZIP Code areas it reaches

The spread is the thing to notice. In 80401 this district holds 100% of the homes; in 80419 it holds no homes at all. Same district, opposite answers, and a lookup that names it without the share tells the second household the same thing as the first.

• ZIP Code 80401 · Golden, Colorado100% of the homes
• ZIP Code 80127 · Dakota Ridge, Colorado100% of the homes
• ZIP Code 80228 · Lakewood, Colorado100% of the homes
• ZIP Code 80004 · Arvada, Colorado100% of the homes
• ZIP Code 80033 · Wheat Ridge, Colorado100% of the homes
• ZIP Code 80005 · Arvada, Colorado100% of the homes
• ZIP Code 80215 · Lakewood, Colorado100% of the homes
• ZIP Code 80465 · Dakota Ridge, Colorado100% of the homes
• ZIP Code 80007 · Arvada, Colorado100% of the homes
• ZIP Code 80433 · Aspen Park, Colorado100% of the homes
• ZIP Code 80454 · Indian Hills, Colorado100% of the homes
• ZIP Code 80457 · Kittredge, Colorado100% of the homes
• ZIP Code 80425 · Jefferson County, Colorado100% of the homes
• ZIP Code 80453 · Idledale, Colorado100% of the homes
• ZIP Code 80232 · Lakewood, Colorado100% of the homes
• ZIP Code 80226 · Lakewood, Colorado99% of the homes
• ZIP Code 80214 · Lakewood, Colorado98% of the homes
• ZIP Code 80002 · Arvada, Colorado96% of the homes
• ZIP Code 80128 · Columbine, Colorado93% of the homes
• ZIP Code 80403 · Coal Creek, Colorado92% of the homes
• ZIP Code 80021 · Westminster, Colorado86% of the homes
• ZIP Code 80003 · Arvada, Colorado85% of the homes
• ZIP Code 80439 · Evergreen, Colorado83% of the homes
• ZIP Code 80227 · Lakewood, Colorado76% of the homes
• ZIP Code 80470 · Jefferson County, Colorado72% of the homes
• ZIP Code 80235 · Denver, Colorado59% of the homes
• ZIP Code 80123 · Columbine, Colorado43% of the homes
• ZIP Code 80020 · Broomfield, Colorado23% of the homes
• ZIP Code 80212 · Denver, Colorado14% of the homes
• ZIP Code 80031 · Westminster, Colorado7.6% of the homes
• ZIP Code 80135 · Roxborough Park, Colorado2.4% of the homes
• ZIP Code 80421 · Park County, Colorado19 homes, under half a percent
• ZIP Code 80125 · Roxborough Park, Colorado1 home, under half a percent
• ZIP Code 80419 · Golden, Coloradono homes at all

The areas it leads without holding most of the homes

Jefferson County School District R-1 is the largest district in 27 ZIP Code areas. Answer with its name alone and the answer misses 26,494 of the 271,717 homes those areas hold — though in 14 of them it holds every home there is. The count is homes, not addresses, and it is the number no lookup prints.

Jefferson County School District R-1 is the largest name in ZIP Code 80123 · Columbine, Colorado and still holds a minority of it: 8,647 of 20,059 homes. The other 11,412 homes are with Denver County School District 1 and Littleton School District 6. This is the shape that makes a one-name answer worst — the name is right for fewer homes than it is wrong for.

ZIP Code 80227 · Lakewood, Colorado is a two-district area: 11,997 of its 15,855 homes are inside Jefferson County School District R-1, and the other 3,858 homes are with Denver County School District 1. Which one an address belongs to is settled by the street, not by the five digits.

In ZIP Code 80021 · Westminster, Colorado the split runs 14,703 to 2,388 and the larger part is Jefferson County School District R-1's: the rest is 2,388 homes with Boulder Valley School District RE-2.

Jefferson County School District R-1 holds 8,325 of the 9,094 homes in ZIP Code 80403 · Coal Creek, Colorado, so its name is right for most of the area and wrong for the rest: 769 homes with Boulder Valley School District RE-2 and Gilpin County School District RE-1.

In ZIP Code 80004 · Arvada, Colorado the single-name answer is the true one: Jefferson County School District R-1 holds all 15,253 homes counted there, and no other district holds a share worth naming.

Jefferson County School District R-1 reaches into ZIP Code 80020 · Broomfield, Colorado with 4,889 of its 21,157 homes; 3 districts there hold a real share of it, and Boulder Valley School District RE-2 leads them. The familiar answer for that area is one of the others, and it is wrong for those 4,889 homes.

ZIP Code 80212 · Denver, Colorado is another area where Jefferson County School District R-1 is present without being the answer: 1,406 of its 10,174 homes, behind Denver County School District 1.

Jefferson County School District R-1 is not the name anyone would give for ZIP Code 80031 · Westminster, Colorado — Westminster Public leads it — and Jefferson County School District R-1 holds 1,155 homes there all the same. Answer that area with one name and that is what it is wrong about.

Who takes the other homes in its ZIP Codes

Jefferson County School District R-1 runs pre-K through grade 12 itself, so an address it holds sees no change of authority between grade school and high school. The districts listed below are the ones that take the other homes in the ZIP Code areas it shares — Denver County School District 1, Boulder Valley School District RE-2 and Westminster Public. They are neighbors on the same postal ground, not the next stop for its own students.

• Denver County School District 120,328 homes in 6 shared ZIP Code areas
• Boulder Valley School District RE-213,757 homes in 3 shared ZIP Code areas
• Westminster Public School District11,358 homes in 4 shared ZIP Code areas
• Adams 12 Five Star Schools11,317 homes in 2 shared ZIP Code areas
• Douglas County School District RE-16,473 homes in 2 shared ZIP Code areas
• Littleton School District 66,358 homes in 2 shared ZIP Code areas

Who it shares ZIP Codes with

Jefferson County School District R-1 shares ZIP Code areas with 9 different districts. The most frequent are Denver County School District 1, Westminster Public, Boulder Valley School District RE-2 and Littleton School District 6. In a neighborhood this crowded the question is not which district serves the ZIP Code but which side of which street an address is on.

• Denver County School District 16 shared ZIP areas
• Westminster Public School District4 shared ZIP areas
• Boulder Valley School District RE-23 shared ZIP areas
• Littleton School District 62 shared ZIP areas
• Adams 12 Five Star Schools2 shared ZIP areas
• Platte Canyon School District 11 shared ZIP area

Where this district sits

• School districts in Colorado234 of 520 ZIP areas split
• Every district with a page here260 districts listed

What to do next

Ask the district office to confirm your street address. A district settles that question on its own site: look for a school locator, a find my school tool, or an attendance zone map. Where there is none, ask the office itself.

A ZIP Code is a set of mail delivery routes, not a boundary: in 16 of the 34 ZIP Code areas Jefferson County School District R-1 reaches, at least one other district holds a real share of the homes as well, and the line between them runs along streets. Only the district can say which side of that line an address is on.

This site links to no district website. None of the federal files it is built from publishes one, and a guessed address is worse than none. It is the district office, not a search engine, that settles an address.

If a house purchase depends on the answer, ask the district itself for written confirmation of that exact address. A listing is not a district record, and neither is this page.

What this cannot tell you

The homes were counted in the 2020 Census and the district lines are the 2026 boundary file. Nothing on this page adjusts one to the other. Where houses have been built or cleared since the count, a share here describes the place as it was counted rather than as it stands today, and in the fastest-growing ZIP Code areas that gap is the largest single source of error on this site.

A share on this page is a share of the homes in the ZIP Code area, not a probability for any particular address. Enrollment is decided by street address, and a district may run magnet, charter or choice programs that ignore the boundary entirely. If a decision depends on the answer, the district office is the only authority; this page shows what the federal boundary files say and when they were published.

A district boundary is not a school attendance zone. This site never says which school an address is assigned to: no current national dataset of attendance zones exists, and the district draws them itself. Nor is anything here endorsed or certified by the Census Bureau; we use their published files, and that is the whole of the relationship.

A ZIP Code is a set of mail delivery routes, not an area. What is mapped here is the Census Bureau's ZIP Code Tabulation Area, the closest published approximation to it. The two are not identical, and a handful of ZIP Codes used only for post office boxes or single buildings have no tabulation area at all.

Where these numbers come from

School district boundaries come from the Census Bureau's Census Geographic Relationship File, current 2026 vintage, which assigns every census block to a unified district or to an elementary and a secondary district. Homes and residents in each block come from the 2020 Census Redistricting Data (PL 94-171), H1_001 and P1_001. The ZIP Code areas come from the same Geographic Relationship File, block to ZIP Code Tabulation Area. District names and grade ranges come from the Census Gazetteer 2025, with 2020 for districts no longer listed.

The place name printed beside a ZIP Code comes from the Census 2020 ZIP Code Tabulation Area relationship files: place, county subdivision and county, taken 2026-09-06. It is a label rather than a measurement: the Census Bureau does not publish which post office a ZIP Code belongs to, so the place named is the one covering the most land inside the area, not the city the Postal Service prints on an envelope.

Everything else on this page — the shares, the counts of districts per ZIP, the comparison between the two grade bands, the rankings — is computed here from those files. The source publishes none of it. Snapshot taken 2026-09-03.