Oldest ZIP codes in Boulder, CO
These are the 6 ZIP codes in Boulder, CO with the highest median age, out of 6 with at least 1,000 residents. 80304 (Boulder, 42.8), 80301 (Boulder, 36.9) and 80305 (Boulder, 36.7) lead the list. There is no single "best" ZIP code in Boulder; the right one depends on who you want to reach, so the same ZIP codes are ranked several ways below.
Oldest ZIP codes in Boulder
| Rank | ZIP | Mailing city | Median age | Residents | Households | Residential mailboxes |
|---|---|---|---|---|---|---|
| 1 | 80304 | Boulder | 42.8 ±2.2 | 25,383 | 11,358 | 12,139 |
| 2 | 80301 | Boulder | 36.9 ±1.7 | 25,007 | 12,371 | 13,814 |
| 3 | 80305 | Boulder | 36.7 ±2.1 | 16,291 | 6,976 | 7,285 |
| 4 | 80303 | Boulder | 29.3 ±1.2 | 24,996 | 11,783 | 12,581 |
| 5 | 80302 | Boulder | 24.9 ±1.5 | 29,569 | 12,425 | 12,329 |
| 6 | 80310 | Boulder | 19.3 ±0.2 | 7,692 | 2 | — |
How we ranked them
Ranked by median age of all residents, highest first (ACS 5-year estimates, 2020–2024). ZIP codes need at least 1,000 residents to be ranked; 6 of 6 qualify.
Which of these to mail, and why
Older ZIP codes respond to health care, hearing and vision, Medicare plans, home safety, estate planning and services that come to the door.
The top five ZIP codes on this list hold 54,913 households, on 114 carrier routes with 58,148 residential mailboxes. Open any of them on the route map to see each carrier route's own figures before you choose.
Open 80304 on the EDDM route map
More rankings
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- ZIP codes with the highest home values in Boulder
- ZIP codes with the highest homeownership in Boulder
- ZIP codes with the most families with kids in Boulder
- ZIP codes with the most new movers in Boulder
- Youngest ZIP codes in Boulder
- Fastest-growing ZIP codes in Boulder
- Oldest ZIP codes in Boulder County
- All Boulder ZIP codes
Businesses that mail these ZIP codes
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EDDM guides
Frequently asked questions
- Which ZIP code in Boulder has the highest median age?
- 80304 (Boulder), at 42.8 (±2.2), among 6 ZIP codes with at least 1,000 residents.
- How is this ranking calculated?
- Ranked by median age of all residents, highest first (ACS 5-year estimates, 2020–2024).
- Why are some ZIP codes missing?
- ZIP codes with fewer than 1,000 residents are left out because their survey estimates swing too much to rank, and so are ZIP codes where the Census Bureau did not publish this figure.
This product uses the Census Bureau Data API but is not endorsed or certified by the Census Bureau.