Every ZIP code in the United States, with weather, radar, trivia and the numbers behind it. Five digits since 1963!

ZIP stands for Zone Improvement Plan. The codes went live on July 1, 1963.The lowest ZIP code is 00501 — the IRS in Holtsville, New York.The highest ZIP code is 99950, in Ketchikan, Alaska.Type 07734 into a calculator and turn it upside down: hELLO. It is Keansburg, New Jersey.12345 belongs to one company: General Electric in Schenectady, New York.The first digit is a region: 0 is New England and New Jersey, 9 is the West Coast, Alaska and Hawaii.Mr. ZIP, the cartoon mailman, was the mascot that sold the idea to America.ZIP+4 arrived in 1983 and can narrow a ZIP down to one side of one block.A ZIP code is a mail route, not a place: plenty of them cross county and even state lines.Play ZIP Hunt: guess the secret ZIP code of the day in six tries.
zipcodes.pro — RANKINGS/CO/HIGHEST-DENSITY

Most Densely Populated ZIP Codes in Colorado

What this measures. People per square mile of land area. Source: Census American Community Survey and Gazetteer, data release 2026-10-12.

# ZIP City County People per sq mi
1 80290 Denver Denver 59,250
2 80203 Denver Denver 20,532
3 80202 Denver Denver 16,080
4 80310 Boulder Boulder 14,114
5 80218 Denver Denver 12,097
6 80247 Denver Denver 10,216
7 80206 Denver Denver 9,840
8 80211 Denver Denver 8,458
9 80010 Aurora Arapahoe 8,258
10 80219 Denver Denver 8,064
11 80209 Denver Denver 7,869
12 80246 Denver Denver 7,838
13 80205 Denver Denver 7,456
14 80231 Denver Denver 7,350
15 80260 Denver Adams 7,281
16 80220 Denver Denver 7,195
17 80012 Aurora Arapahoe 6,717
18 80237 Denver Denver 6,453
19 80204 Denver Denver 6,444
20 80210 Denver Denver 6,424
21 80222 Denver Denver 6,232
22 80232 Denver Jefferson 5,935
23 80224 Denver Denver 5,902
24 80030 Westminster Adams 5,848
25 80212 Denver Denver 5,823
26 80214 Denver Jefferson 5,788
27 80014 Aurora Arapahoe 5,513
28 80207 Denver Denver 5,495
29 80003 Arvada Jefferson 5,468
30 80917 Colorado Springs El Paso 5,415
31 80233 Denver Adams 5,299
32 80013 Aurora Arapahoe 5,252
33 80236 Denver Denver 5,250
34 80922 Colorado Springs El Paso 5,225
35 80241 Thornton Adams 5,184
36 80910 Colorado Springs El Paso 5,134
37 80004 Arvada Jefferson 4,713
38 80923 Colorado Springs El Paso 4,549
39 80122 Littleton Arapahoe 4,526
40 80238 Denver Denver 4,502
41 80909 Colorado Springs El Paso 4,475
42 80015 Aurora Arapahoe 4,446
43 80017 Aurora Arapahoe 4,427
44 80229 Denver Adams 4,404
45 80221 Denver Adams 4,368
46 80239 Denver Denver 4,351
47 80129 Littleton Douglas 4,293
48 80031 Westminster Adams 4,222
49 80918 Colorado Springs El Paso 4,173
50 80234 Denver Adams 4,168

Showing the top 50 of 527 ZIP codes in Colorado that have this figure . 80290 ranks 1st at 59,250, against 4,168 in 50th place.

Other rankings for Colorado

Cite this page

zipcodes.pro. “Most Densely Populated ZIP Codes in Colorado.” Data release 2026-10-12. Retrieved 2026-10-20. https://zipcodes.pro/rankings/co/highest-density

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