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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/78664

78664

ZIP 78664 is in Round Rock, Texas, mostly in Williamson County; area codes 512 and 737; Central time. Round Rock has 6 ZIP codes; the others are 78665, 78680, 78681, 78682 and 78683.

Type
Standard
Time zone
America/Chicago
County
Williamson +1 more
Population
62,060
Coordinates
30.5054, -97.6473
☼ Live from 78664 — Round Rock, TX

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Where 78664 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 78664
  • 🔢 Type 78664 into a pocket calculator and turn it upside down: hggBL — not quite a word, sorry.
  • ➕ As a number, 78,664 = 2 × 2 × 2 × 9833. Its digits add up to 31, a total 799 other ZIP codes share.
  • 💾In binary, the way a computer stores it: 10011001101001000
  • 🏠 Its numerical neighbours: 78663 (Round Mountain, TX, 40 mi away) and 78665 (Round Rock, TX, 3 mi away).
  • 🔄 Backwards, 78664 becomes 46687, which is not a ZIP code at all.
  • 👥 25 other ZIP codes are made of exactly the same digits (46786, 46867, 47866, 48667, 48766, 64867, …). The farthest-flung twin is 48766 in Twining, MI, 1,204 miles away.
  • 🧭 Farther south than 91% of all ZIP codes, and farther west than 76%.
  • 🎯646 miles south of the geographic center of the Lower 48, near Lebanon, Kansas.
  • 🌏 Dig straight through the Earth from 78664 and you would come out at 30.51°S, 82.35°E — 1,448 miles from Port-aux-Français, French Southern Territories, the nearest big city to that spot.
  • ☀Longest day of the year: 14h 07m of daylight. Shortest: 10h 10m.
  • 📏 At 16.6 square miles of land, 78664 is bigger than 34% of ZIP codes — room for about 13 Central Parks.
🌙 The sky over 78664 today
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🌋 Shake report
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Source: USGS.

People and housing

Population62,060This ZIP62,060
Households23,484This ZIP23,484
Housing units24,497This ZIP24,497
Median age35.1This ZIP35.1Texas35.6US 38.9
Median household income$87,417This ZIP$87,417Texas$78,476US $80,734
Median home value$358,200This ZIP$358,200Texas$283,800US $332,700
Median gross rent$1,692This ZIP$1,692Texas$1,403US $1,413
Bachelor's degree or higher36.4%This ZIP36.4%
Mean commute25.6 minThis ZIP25.6 min
Population density3,735.9 / sq miThis ZIP3,735.9 / sq mi

Business and tax activity

Business establishments1,841This ZIP1,841
Employees28,470This ZIP28,470
Annual payroll$1,649,775,000This ZIP$1,649,775,000
Tax returns filed27,970This ZIP27,970
Total adjusted gross income$2,216,171,000This ZIP$2,216,171,000

Land area

Land area16.61 sq miThis ZIP16.61 sq mi
Water area0.09 sq miThis ZIP0.09 sq mi

Counties 78664 spans

A ZIP code is a mail route and ignores county lines. Shares are by overlapping land area.

CountyShare of this ZIP
Williamson County 85.6%
Travis County 14.4%

Other place names in 78664

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

ZIP codes near 78664

ZIPCityDistance
78665 Round Rock, TX 3.1 mi
78764 Austin, TX 4.2 mi
78728 Austin, TX 4.3 mi
78681 Round Rock, TX 4.8 mi
78691 Pflugerville, TX 4.8 mi
78660 Pflugerville, TX 5.5 mi
78717 Austin, TX 6.4 mi
78727 Austin, TX 6.7 mi
78634 Hutto, TX 7.2 mi
78729 Austin, TX 7.3 mi

Find every ZIP code within 10 miles of 78664 →

Questions about this ZIP code

Where is ZIP code 78664?

78664 is in Round Rock, Texas, in Williamson County, part of the Austin-Round Rock-San Marcos, TX metropolitan area. Its published point location is 30.5054, -97.6473.

What county is 78664 in?

78664 spans 2 counties: Williamson County and Travis County. Most of it falls in Williamson County, measured by overlapping land area — the county holding the most land in a ZIP code is not always the one holding the most residents.

What area code is 78664?

Round Rock uses area codes 512 and 737, from NANPA's telephone records.

What time zone is 78664 in?

78664 uses America/Chicago.

How many people live in 78664?

About 62,060 people live in ZIP code 78664, in 23,484 households, at 3,735.9 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 78664?

$87,417 a year, against $78,476 across Texas.

What ZIP codes are near 78664?

The closest are 78665 (3.1 mi), 78764 (4.2 mi), 78728 (4.3 mi), 78681 (4.8 mi) and 78691 (4.8 mi).

Is 78664 a PO Box ZIP code?

78664 is a standard ZIP code. A normal ZIP code with street delivery.

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Cite this page

zipcodes.pro. “78664 ZIP Code — Round Rock, Texas (Williamson County).” Data release 2026-10-12. Retrieved 2026-10-20. https://zipcodes.pro/zip/78664

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