Below is a list of Stephenson County IL zip codes. For your research we have also included Stephenson County Area Code, Time Zone, UTC and the local County FIPS Code. Each Stephenson County Illinois zip code has a center Longitude / Latitude point (the Stephenson County center is -89.652900695801 / 42.367500305176). For your convenience we have also indicated if that zip code in Stephenson County observes Daylight Savings time.