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/CT/HIGHEST-DENSITY

Most Densely Populated ZIP Codes in Connecticut

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 06901 Stamford Fairfield 21,684
2 06510 New Haven New Haven 17,041
3 06080 Suffield Hartford 12,150
4 06608 Bridgeport Fairfield 11,815
5 06605 Bridgeport Fairfield 11,343
6 06710 Waterbury New Haven 10,260
7 06604 Bridgeport Fairfield 10,070
8 06511 New Haven New Haven 9,415
9 06606 Bridgeport Fairfield 9,335
10 06519 New Haven New Haven 8,821
11 06106 Hartford Hartford 8,719
12 06105 Hartford Hartford 8,462
13 06112 Hartford Hartford 7,522
14 06902 Stamford Fairfield 7,317
15 06051 New Britain Hartford 7,200
16 06610 Bridgeport Fairfield 7,152
17 06119 West Hartford Hartford 7,102
18 06607 Bridgeport Fairfield 6,902
19 06906 Stamford Fairfield 6,819
20 06854 Norwalk Fairfield 6,679
21 06114 Hartford Hartford 6,541
22 06269 Storrs Mansfield Tolland 6,366
23 06513 New Haven New Haven 5,385
24 06516 West Haven New Haven 5,149
25 06103 Hartford Hartford 5,085
26 06320 New London New London 4,921
27 06053 New Britain Hartford 4,627
28 06907 Stamford Fairfield 4,448
29 06705 Waterbury New Haven 4,447
30 06702 Waterbury New Haven 4,404
31 06515 New Haven New Haven 4,170
32 06905 Stamford Fairfield 4,087
33 06706 Waterbury New Haven 4,073
34 06120 Hartford Hartford 3,944
35 06704 Waterbury New Haven 3,924
36 06110 West Hartford Hartford 3,884
37 06855 Norwalk Fairfield 3,786
38 06459 Middletown Middlesex 3,718
39 06851 Norwalk Fairfield 3,625
40 06870 Old Greenwich Fairfield 3,469
41 06878 Riverside Fairfield 3,444
42 06376 South Lyme New London 3,296
43 06825 Fairfield Fairfield 3,235
44 06263 Rogers Windham 3,234
45 06614 Stratford Fairfield 3,219
46 06401 Ansonia New Haven 3,205
47 06708 Waterbury New Haven 3,132
48 06387 Wauregan Windham 3,069
49 06052 New Britain Hartford 3,053
50 06460 Milford New Haven 3,029

Showing the top 50 of 288 ZIP codes in Connecticut that have this figure . 06901 ranks 1st at 21,684, against 3,029 in 50th place.

Other rankings for Connecticut

Cite this page

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

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