This is the Illinois ZIP code website, which contains 1,579 ZIP codes, 1,409 cities, 102 counties, and more than 1,702,831 ZIP+4 codes. Each 9-digit ZIP code corresponds to one or several Illinois addresses.
Besides, there are also some tools related to ZIP code or address. For example, address verification, full ZIP code search, random address generator, etc.

State-image: il

Cities in Illinois


Please check ZIP Codes by City Name:

Counties in Illinois


How to write a U.S. envelope?

  • First, you need to fill in the recipient's mailing information in the center of the envelope. The first line is the recipient's name, the second line is the street address with a detailed house number, and the last line is the city, state abbr, and ZIP Code.

    Second, write the sender's information on the left top corner of the envelope. If your mail cannot be delivered, it will return to the sender's address.

    Finally, don't forget to stick the stamp on the right top corner. Otherwise, the letter will not go into the delivery process.

    Here is the envelope example below.

    ZIP Code: homepage
  • United States Envelope Example

For more explanation, please read the official document: USA.pdf (English)



The population of the state Illinois was 12,830,632 in 2010 and reached 12,671,821 in 2019 with an increase of –158,811. Now the state Illinois is the 6th state by population size in the U.S. and accounts for 3.82% of the total U.S. population.

Area2019 Census Data2010 Census DataIncreaseIncrease(%)RankProportion of total population(%)