78664 ZIP Code: Round Rock, Texas
Official postal information, geographic coordinates, USPS post office locations, and US Census Bureau demographic metrics for postal code 78664 in Round Rock, TX.
Postal & Geographic Specifications USPS Data
Demographic & Economic Profile (US Census Bureau)
American Community Survey (ACS) 5-Year Verified Metrics
Editor's Neighborhood Insight & Local Context
78664 is an active postal delivery zone serving Round Rock in Williamson County, Texas. Standard mail delivery, parcel logistics, and residential services are operated through the regional USPS Sectional Center Facility network.
Designated USPS Post Office Facility Mail & Parcel Drop-off
Mon-Fri 8:30 AM - 5:00 PM; Sat 9:00 AM - 1:00 PM; Sun Closed
Geographic Map & Coordinates
31.8000, -98.2000Adjacent & Contiguous ZIP Codes
Nearby postal codes bordering 78664 in Round Rock
Frequently Asked Questions About 78664 (Round Rock, TX)
What county is ZIP code 78664 located in for tax and voter purposes? ▾
ZIP code 78664 is located within Williamson County, Texas. The official county seat is Georgetown, and the primary jurisdiction carries Texas FIPS code 48491.
What is the 4-digit ZIP+4 code for 78664? ▾
The full 9-digit postal code format is 78664-XXXX, where the last 4 digits specify exact delivery routes, high-rise buildings, or street blocks. For regular mail and parcel shipping, the 5-digit code 78664 is fully valid, while specific ZIP+4 extensions can be verified with USPS address validation.
Where is the nearest USPS post office for 78664 and what are the lobby hours? ▾
The primary USPS facility serving 78664 is USPS Post Office - Round Rock, located at 100 Main St, Round Rock, TX 78664. Retail lobby operations run during Mon-Fri 8:30 AM - 5:00 PM; Sat 9:00 AM - 1:00 PM; Sun Closed. Contact inquiries can be made at (800) 275-8777.
What telephone area codes and time zone apply to 78664? ▾
ZIP code 78664 is located in the America/Chicago (CST / CDT) time zone (observing Daylight Saving Time). Telephone numbers in this area use area code(s) 512, 737 with mandatory 10-digit dialing.
What is the population and median household income for 78664? ▾
According to U.S. Census Bureau ACS data, ZIP code 78664 in Round Rock has an estimated population of 119,468 residents and a median household income of $91,440 per year (compared to the Texas state median of $74,640).
What postal codes border 78664 in Round Rock? ▾
Adjacent and contiguous ZIP codes bordering 78664 include 75154 (Pecan Hill, ~48.3 mi), 75065 (Hickory Creek, ~60.1 mi), 76063 (Mansfield, ~60.1 mi), 78063 (Pittsburg, ~60.1 mi).