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 — PREFIX/603

ZIP codes starting with 603

ZIP codes
6
States
IL
Largest city
Oak Park, IL
Population
65,284

The first three digits of a ZIP code identify a sectional center facility — the postal processing plant that sorts mail for the area. It is a mail-routing grouping, not an administrative boundary.

Every ZIP code in 603xx

ZIP codes starting with 603
ZIP City Type Population Median income Median home
60301 Oak Park , IL Standard 3,475 $99,167 $247,000
60302 Oak Park , IL Standard 32,862 $100,680 $474,200
60303 Oak Park , IL No street area — — —
60304 Oak Park , IL Standard 16,955 $136,178 $466,700
60305 River Forest , IL Standard 11,992 $146,786 $687,300
60399 Wood Dale , IL No street area — — —

Cite this page

zipcodes.pro. “ZIP codes starting with 603.” Data release 2026-10-12. Retrieved 2026-10-20. https://zipcodes.pro/prefix/603

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