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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 — ZIP/91001

91001

ZIP 91001 is in Altadena, California, in Los Angeles County; area codes 626, 818 and 747; Pacific time. Altadena has 2 ZIP codes; the other is 91003.

Type
Standard
Time zone
America/Los_Angeles
County
Los Angeles
Population
35,475
Coordinates
34.1945, -118.1383
☼ Live from 91001 — Altadena, CA

Weather right now

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Local time: —

Where 91001 is

Approximate ZIP boundary (Census ZCTA 2020). ZIP codes are mail routes, not areas, so the shape shown is the Census tabulation area that approximates it.

★ Weird and wonderful facts about 91001
  • 🔢 Type 91001 into a pocket calculator and turn it upside down: IOOIG — not quite a word, sorry.
  • ➕ As a number, 91,001 = 17 × 53 × 101. Its digits add up to 11, a total 714 other ZIP codes share.
  • 💾In binary, the way a computer stores it: 10110001101111001
  • 🏠 Its numerical neighbours: 90899 (Long Beach, CA, 30 mi away) and 91003 (Altadena, CA, 1 mi away).
  • 🔄 Backwards, 91001 becomes 10019 — and that is a real ZIP code: New York, NY, 2,437 miles away.
  • 👥 13 other ZIP codes are made of exactly the same digits (00911, 01109, 01901, 01910, 09110, 10019, …). The farthest-flung twin is 09110 in APO AE, a military post office, 5,772 miles away.
  • 🧭 Farther south than 78% of all ZIP codes, and farther west than 91%.
  • 🎯1,144 miles west of the geographic center of the Lower 48, near Lebanon, Kansas.
  • 🌏 Dig straight through the Earth from 91001 and you would come out at 34.19°S, 61.86°E — 1,000 miles from Saint-Denis, Reunion, the nearest big city to that spot.
  • ☀Longest day of the year: 14h 26m of daylight. Shortest: 9h 52m.
  • 📏 At 8.3 square miles of land, 91001 is bigger than 25% of ZIP codes — room for about 6.3 Central Parks.
🌙 The sky over 91001 today
  • Working out the sun…
🌋 Shake report
  • Checking the USGS…

Source: USGS.

People and housing

Population35,475This ZIP35,475
Households12,587This ZIP12,587
Housing units13,216This ZIP13,216
Median age46.3This ZIP46.3California37.9US 38.9
Median household income$134,903This ZIP$134,903California$99,122US $80,734
Median home value$1,135,200This ZIP$1,135,200California$734,700US $332,700
Median gross rent$2,437This ZIP$2,437California$2,036US $1,413
Bachelor's degree or higher53.9%This ZIP53.9%
Mean commute28.0 minThis ZIP28.0 min
Population density4,294.8 / sq miThis ZIP4,294.8 / sq mi

Business and tax activity

Business establishments752This ZIP752
Employees4,913This ZIP4,913
Annual payroll$282,507,000This ZIP$282,507,000
Tax returns filed17,260This ZIP17,260
Total adjusted gross income$2,304,418,000This ZIP$2,304,418,000

Land area

Land area8.26 sq miThis ZIP8.26 sq mi
Water area0.04 sq miThis ZIP0.04 sq mi

Other place names in 91001

Census places whose land this ZIP code overlaps. The Postal Service may accept other city names in an address, too.

ZIP codes near 91001

ZIPCityDistance
91003 Altadena, CA 0.5 mi
91104 Pasadena, CA 2.2 mi
91103 Pasadena, CA 2.4 mi
91012 La Canada Flintridge, CA 2.9 mi
91199 Pasadena, CA 3.2 mi
91102 Pasadena, CA 3.2 mi
91109 Pasadena, CA 3.2 mi
91110 Pasadena, CA 3.2 mi
91114 Pasadena, CA 3.2 mi
91115 Pasadena, CA 3.2 mi

Find every ZIP code within 10 miles of 91001 →

Questions about this ZIP code

Where is ZIP code 91001?

91001 is in Altadena, California, in Los Angeles County, part of the Los Angeles-Long Beach-Anaheim, CA metropolitan area. Its published point location is 34.1945, -118.1383.

What county is 91001 in?

91001 lies in Los Angeles County.

What area code is 91001?

Altadena uses area codes 626, 818 and 747, from NANPA's telephone records.

What time zone is 91001 in?

91001 uses America/Los_Angeles.

How many people live in 91001?

About 35,475 people live in ZIP code 91001, in 12,587 households, at 4,294.8 people per square mile. These are American Community Survey 5-year estimates for the ZIP Code Tabulation Area, not a headcount.

What is the median household income in 91001?

$134,903 a year, against $99,122 across California.

What ZIP codes are near 91001?

The closest are 91003 (0.5 mi), 91104 (2.2 mi), 91103 (2.4 mi), 91012 (2.9 mi) and 91199 (3.2 mi).

Is 91001 a PO Box ZIP code?

91001 is a standard ZIP code. A normal ZIP code with street delivery.

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Cite this page

zipcodes.pro. “91001 ZIP Code — Altadena, California (Los Angeles County).” Data release 2026-10-12. Retrieved 2026-10-20. https://zipcodes.pro/zip/91001

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