Denver ZIP Codes: The Full List, and the 11 That Sit Outside Denver County

All 66 ZIP codes USPS assigns to Denver

Of the 66 ZIP codes with "Denver, CO" as the primary USPS place name, this site's source data places 55 in Denver County itself, six in Jefferson County, and five in Adams County. zipcodestogo.com's Denver city page lists 64 codes for comparison: close to this site's 66, but not identical, which is typical: independent ZIP directories routinely disagree by a handful of codes depending on whether they count PO-Box-only or otherwise non-standard codes the same way. Denver's 11-ZIP spillover into two neighboring counties is a modest version of a much bigger split elsewhere on this site: Kansas City's ZIP list splits across two different cities in two different states entirely, not just two counties in one.

How Denver became a county unto itself in 1902

Denver started out inside Arapahoe County, one of the 17 original counties the Colorado General Assembly created on November 1, 1861, with Denver City serving as the county seat. That arrangement lasted forty years. In 1901, the legislature voted to split Arapahoe County three ways: a new, consolidated City and County of Denver; a new Adams County to the north, named for Alva Adams, a five-time gubernatorial candidate who'd already served two terms in the office (1887-89 and 1897-99) and would return for a brief third in early 1905; and the rump of the old county, temporarily renamed South Arapahoe County. Adams wasn't the sitting governor when any of this actually happened, though: that was James B. Orman, who held the office from January 1901 to January 1903 and designated Brighton as Adams County's temporary seat once a Colorado Supreme Court ruling, follow-up legislation, and a referendum let the split take effect on November 15, 1902. South Arapahoe County's name didn't even last a full year: the legislature changed it back to plain Arapahoe County on April 11, 1903, with its seat relocated to Littleton.

Jefferson County, the source of this site's other six Denver ZIP codes, wasn't part of that 1902 reorganization at all. It's one of the same 17 counties created alongside the original Arapahoe County back in 1861, sitting immediately to Denver's west with its own county seat at Golden. So the Jefferson County ZIP codes on the list above aren't a product of Denver's consolidation; they're a reminder that Denver, like Atlanta on this site's ZIP list for Atlanta, simply has USPS delivery routes that cross into a neighboring county that's always been there, regardless of where Denver's government boundary actually sits.

Six ZIPs west in Jefferson County, five north in Adams

The six Jefferson County ZIP codes on Denver's list (80214, 80215, 80225, 80226, 80228, and 80232) sit in the corridor just west of downtown, an area covered mostly by Lakewood, Jefferson County's largest city, along with slivers of Wheat Ridge and Edgewater. Per unitedstateszipcodes.org's boundary data, 80214 in particular splits across several place names at once: Lakewood, Edgewater, and Wheat Ridge all draw from it. That's a reminder that a single "place" label on a ZIP code, whether it reads Denver or something else, can mask a boundary that a postal carrier's route crosses more than once.

The five Adams County ZIP codes (80221, 80229, 80233, 80234, and 80260) sit north of downtown, in the Federal Heights, Thornton, and Northglenn corridor. 80221 is the one worth a caveat: unitedstateszipcodes.org's boundary data shows it straddling both Adams and Denver counties at once, with Adams holding the larger share. This site's table above, like GeoNames' broader dataset, assigns each ZIP code to a single county, so 80221 shows up here as Adams only, the same kind of simplification this site flagged on the Atlanta ZIP list, where one ZIP straddling Fulton and Cobb counties got flattened into a single row too.