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/WI/HIGHEST-DENSITY

Most Densely Populated ZIP Codes in Wisconsin

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 53703 Madison Dane 20,356
2 54307 Green Bay Brown 13,429
3 53204 Milwaukee Milwaukee 12,402
4 53202 Milwaukee Milwaukee 12,233
5 53715 Madison Dane 12,074
6 53215 Milwaukee Milwaukee 10,541
7 53706 Madison Dane 9,446
8 53210 Milwaukee Milwaukee 9,359
9 53726 Madison Dane 8,942
10 53211 Milwaukee Milwaukee 8,634
11 53233 Milwaukee Milwaukee 8,270
12 53206 Milwaukee Milwaukee 7,499
13 53212 Milwaukee Milwaukee 7,107
14 53218 Milwaukee Milwaukee 7,024
15 53219 Milwaukee Milwaukee 6,892
16 53213 Milwaukee Milwaukee 6,872
17 53216 Milwaukee Milwaukee 6,582
18 53208 Milwaukee Milwaukee 6,438
19 53205 Milwaukee Milwaukee 6,412
20 54946 King Waupaca 5,729
21 53203 Milwaukee Milwaukee 5,309
22 53143 Kenosha Kenosha 5,042
23 53220 Milwaukee Milwaukee 5,003
24 53214 Milwaukee Milwaukee 4,829
25 53222 Milwaukee Milwaukee 4,567
26 53227 Milwaukee Milwaukee 4,472
27 53172 South Milwaukee Milwaukee 4,236
28 53221 Milwaukee Milwaukee 4,223
29 53209 Milwaukee Milwaukee 4,149
30 53405 Racine Racine 4,053
31 53705 Madison Dane 3,963
32 53140 Kenosha Kenosha 3,832
33 53110 Cudahy Milwaukee 3,747
34 53225 Milwaukee Milwaukee 3,606
35 53717 Madison Dane 3,588
36 53235 Saint Francis Milwaukee 3,516
37 53714 Madison Dane 3,474
38 53207 Milwaukee Milwaukee 3,448
39 54136 Kimberly Outagamie 3,437
40 53719 Madison Dane 3,352
41 54301 Green Bay Brown 3,343
42 54302 Green Bay Brown 3,288
43 54911 Appleton Outagamie 3,004
44 54915 Appleton Calumet 2,950
45 53716 Madison Dane 2,933
46 53223 Milwaukee Milwaukee 2,921
47 53228 Milwaukee Milwaukee 2,881
48 53031 Hingham Sheboygan 2,838
49 53129 Greendale Milwaukee 2,829
50 53404 Racine Racine 2,795

Showing the top 50 of 783 ZIP codes in Wisconsin that have this figure . 53703 ranks 1st at 20,356, against 2,795 in 50th place.

Other rankings for Wisconsin

Cite this page

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

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