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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/63121

63121

ZIP 63121 is in Saint Louis, Missouri, in St. Louis County; area codes 314 and 557; Central time. Saint Louis has 68 ZIP codes in all.

Type
Standard
Time zone
America/Chicago
County
St. Louis
Metro area
St. Louis, MO-IL
Population
25,008
Coordinates
38.7081, -90.3006
☼ Live from 63121 — Saint Louis, MO

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Where 63121 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 63121
  • 🔢 Type 63121 into a pocket calculator and turn it upside down: IZIEg — not quite a word, sorry.
  • ➕ As a number, 63,121 = 17 × 47 × 79. Its digits add up to 13, a total 1,179 other ZIP codes share.
  • 💾In binary, the way a computer stores it: 1111011010010001
  • 🏠 Its numerical neighbours: 63120 (Saint Louis, MO, 2 mi away) and 63122 (Saint Louis, MO, 11 mi away).
  • 🔄 Backwards, 63121 becomes 12136 — and that is a real ZIP code: Old Chatham, NY, 913 miles away.
  • 👥 31 other ZIP codes are made of exactly the same digits (11236, 11362, 12136, 13126, 13162, 13261, …). The farthest-flung twin is 12136 in Old Chatham, NY, 913 miles away.
  • 🧭 Farther south than 53% of all ZIP codes, and farther west than 57%.
  • 🎯449 miles east of the geographic center of the Lower 48, near Lebanon, Kansas.
  • 🌏 Dig straight through the Earth from 63121 and you would come out at 38.71°S, 89.70°E — 1,209 miles from Port-aux-Français, French Southern Territories, the nearest big city to that spot.
  • ☀Longest day of the year: 14h 53m of daylight. Shortest: 9h 27m.
  • 📏 At 6.8 square miles of land, 63121 is bigger than 22% of ZIP codes — room for about 5.1 Central Parks.
🌙 The sky over 63121 today
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🌋 Shake report
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Source: USGS.

People and housing

Population25,008This ZIP25,008
Households11,142This ZIP11,142
Housing units13,008This ZIP13,008
Median age33.2This ZIP33.2Missouri39.0US 38.9
Median household income$42,701This ZIP$42,701Missouri$70,702US $80,734
Median home value$95,600This ZIP$95,600Missouri$230,300US $332,700
Median gross rent$985This ZIP$985Missouri$1,033US $1,413
Bachelor's degree or higher24.2%This ZIP24.2%
Mean commute23.8 minThis ZIP23.8 min
Population density3,693.4 / sq miThis ZIP3,693.4 / sq mi

Business and tax activity

Business establishments315This ZIP315
Employees4,540This ZIP4,540
Annual payroll$364,428,000This ZIP$364,428,000
Tax returns filed10,310This ZIP10,310
Total adjusted gross income$423,580,000This ZIP$423,580,000

Land area

Land area6.77 sq miThis ZIP6.77 sq mi
Water area0.00 sq miThis ZIP0.00 sq mi

Other place names in 63121

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

ZIP codes near 63121

ZIPCityDistance
63133 Saint Louis, MO 1.8 mi
63120 Saint Louis, MO 2.4 mi
63140 Saint Louis, MO 2.5 mi
63135 Saint Louis, MO 3.0 mi
63130 Saint Louis, MO 3.3 mi
63134 Saint Louis, MO 3.3 mi
63136 Saint Louis, MO 3.4 mi
63114 Saint Louis, MO 3.4 mi
63112 Saint Louis, MO 3.5 mi
63115 Saint Louis, MO 3.7 mi

Find every ZIP code within 10 miles of 63121 →

Questions about this ZIP code

Where is ZIP code 63121?

63121 is in Saint Louis, Missouri, in St. Louis County, part of the St. Louis, MO-IL metropolitan area. Its published point location is 38.7081, -90.3006.

What county is 63121 in?

63121 lies in St. Louis County.

What area code is 63121?

Saint Louis uses area codes 314 and 557, from NANPA's telephone records.

What time zone is 63121 in?

63121 uses America/Chicago.

How many people live in 63121?

About 25,008 people live in ZIP code 63121, in 11,142 households, at 3,693.4 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 63121?

$42,701 a year, against $70,702 across Missouri.

What ZIP codes are near 63121?

The closest are 63133 (1.8 mi), 63120 (2.4 mi), 63140 (2.5 mi), 63135 (3 mi) and 63130 (3.3 mi).

Is 63121 a PO Box ZIP code?

63121 is a standard ZIP code. A normal ZIP code with street delivery.

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Cite this page

zipcodes.pro. “63121 ZIP Code — Saint Louis, Missouri (St. Louis County).” Data release 2026-10-12. Retrieved 2026-10-20. https://zipcodes.pro/zip/63121

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