Before we even get to the most-monied zip codes in Illinois, one quick question for you:Do you know what "zip" in zip code stands for? The term was introduced by the US Postal Service in 1963 when they created the ZIP Code system to make mail delivery faster and more efficient. Topping the list is ZIP code 60043 (Village of Kenilworth), with an average household income of $460,411 and a median of $250,001. Closely following are ZIP code 60022 in Glencoe (average $416,080; median $250,001) and 60093 in Winnetka (average $380,923; median $230,777). Overall, the threshold to crack the top ten was an average household income above roughly $249,000.