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/CA/HIGHEST-DENSITY

Most Densely Populated ZIP Codes in California

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 94102 San Francisco San Francisco 54,344
2 90057 Los Angeles Los Angeles 52,988
3 94109 San Francisco San Francisco 50,559
4 94108 San Francisco San Francisco 43,818
5 90017 Los Angeles Los Angeles 42,676
6 94133 San Francisco San Francisco 36,176
7 90020 Los Angeles Los Angeles 35,067
8 90014 Los Angeles Los Angeles 34,194
9 90005 Los Angeles Los Angeles 33,171
10 94115 San Francisco San Francisco 28,723
11 90006 Los Angeles Los Angeles 28,711
12 94117 San Francisco San Francisco 28,391
13 94105 San Francisco San Francisco 28,116
14 94110 San Francisco San Francisco 27,977
15 94704 Berkeley Alameda 27,953
16 94103 San Francisco San Francisco 25,447
17 90029 Los Angeles Los Angeles 24,203
18 94114 San Francisco San Francisco 23,841
19 94112 San Francisco San Francisco 23,757
20 90011 Los Angeles Los Angeles 23,342
21 91046 Verdugo City Los Angeles 23,000
22 90037 Los Angeles Los Angeles 22,674
23 94123 San Francisco San Francisco 22,418
24 90028 Los Angeles Los Angeles 21,762
25 95053 Santa Clara Santa Clara 20,742
26 94158 San Francisco San Francisco 20,571
27 90270 Maywood Los Angeles 20,368
28 90013 Los Angeles Los Angeles 20,365
29 94118 San Francisco San Francisco 19,516
30 90003 Los Angeles Los Angeles 19,328
31 91203 Glendale Los Angeles 19,198
32 90004 Los Angeles Los Angeles 19,169
33 94612 Oakland Alameda 18,972
34 90255 Huntington Park Los Angeles 18,612
35 90044 Los Angeles Los Angeles 18,587
36 90034 Los Angeles Los Angeles 18,405
37 90025 Los Angeles Los Angeles 18,231
38 91205 Glendale Los Angeles 18,076
39 94709 Berkeley Alameda 17,968
40 91402 Panorama City Los Angeles 17,647
41 90804 Long Beach Los Angeles 17,636
42 90038 Los Angeles Los Angeles 17,524
43 94107 San Francisco San Francisco 17,428
44 90002 Los Angeles Los Angeles 17,415
45 90024 Los Angeles Los Angeles 17,376
46 94116 San Francisco San Francisco 17,336
47 94606 Oakland Alameda 17,182
48 90062 Los Angeles Los Angeles 17,146
49 94122 San Francisco San Francisco 17,138
50 90001 Los Angeles Los Angeles 17,131

Showing the top 50 of 1,802 ZIP codes in California that have this figure . 94102 ranks 1st at 54,344, against 17,131 in 50th place.

Other rankings for California

Cite this page

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

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