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 — ZIP/91021

91021

ZIP 91021 is in Montrose, California, in Los Angeles County; area codes 818 and 747; Pacific time. Montrose has 2 ZIP codes; the other is 91020.

Type
No street area
Time zone
America/Los_Angeles
County
Los Angeles
Coordinates
34.2064, -118.2242

The Census map gives this ZIP code no delivery area of its own, which usually means it serves post office boxes, a single organization or a post office rather than streets of homes.

This ZIP code has no Census tabulation area of its own. Its point falls inside ZCTA 91020, whose figures describe that area — not this ZIP code.

☼ Live from 91021 — Montrose, CA

Weather right now

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Where 91021 is

This ZIP code has no Census tabulation area, so there is no boundary to draw — the marker is its published point location.

★ Weird and wonderful facts about 91021
  • 🔢 Type 91021 into a pocket calculator and turn it upside down: IZOIG — not quite a word, sorry.
  • ➕ As a number, 91,021 = 7 × 13003. Its digits add up to 13, a total 1,179 other ZIP codes share.
  • 💾In binary, the way a computer stores it: 10110001110001101
  • 🏠 Its numerical neighbours: 91020 (Montrose, CA, 1 mi away) and 91023 (Mount Wilson, CA, 9 mi away).
  • 🔄 Backwards, 91021 becomes 12019 — and that is a real ZIP code: Ballston Lake, NY, 2,440 miles away.
  • 👥 32 other ZIP codes are made of exactly the same digits (01129, 01921, 02119, 02191, 02911, 09112, …). The farthest-flung twin is 09112 in APO AE, a military post office, 5,797 miles away.
  • 🧭 Farther south than 77% of all ZIP codes, and farther west than 91%.
  • 🎯1,148 miles west of the geographic center of the Lower 48, near Lebanon, Kansas.
  • 🌏 Dig straight through the Earth from 91021 and you would come out at 34.21°S, 61.78°E — 998 miles from Saint-Denis, Reunion, the nearest big city to that spot.
  • ☀Longest day of the year: 14h 26m of daylight. Shortest: 9h 52m.
🌙 The sky over 91021 today
  • Working out the sun…
🌋 Shake report
  • Checking the USGS…

Source: USGS.

Business and tax activity

Business establishments9This ZIP9
Employees9This ZIP9
Annual payroll$505,000This ZIP$505,000

Land area

ZIP codes near 91021

ZIPCityDistance
91020 Montrose, CA 0.5 mi
91046 Verdugo City, CA 1.0 mi
91011 La Canada Flintridge, CA 1.5 mi
91224 La Crescenta, CA 1.5 mi
91208 Glendale, CA 1.7 mi
91012 La Canada Flintridge, CA 2.1 mi
91214 La Crescenta, CA 2.4 mi
91202 Glendale, CA 2.8 mi
91207 Glendale, CA 2.9 mi
91206 Glendale, CA 3.2 mi

Find every ZIP code within 10 miles of 91021 →

Questions about this ZIP code

Where is ZIP code 91021?

91021 is in Montrose, California, in Los Angeles County, part of the Los Angeles-Long Beach-Anaheim, CA metropolitan area. Its published point location is 34.2064, -118.2242.

What county is 91021 in?

91021 lies in Los Angeles County.

What area code is 91021?

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

What time zone is 91021 in?

91021 uses America/Los_Angeles.

What ZIP codes are near 91021?

The closest are 91020 (0.5 mi), 91046 (1 mi), 91011 (1.5 mi), 91224 (1.5 mi) and 91208 (1.7 mi).

Is 91021 a PO Box ZIP code?

Possibly. The Census map gives this ZIP code no delivery area of its own, which usually means it serves post office boxes, a single organization or a post office rather than streets of homes.

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Cite this page

zipcodes.pro. “91021 ZIP Code — Montrose, California (Los Angeles County).” Data release 2026-10-12. Retrieved 2026-10-20. https://zipcodes.pro/zip/91021

Machine-readable version of these facts:

curl https://zipcodes.pro/zip/91021.json

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