Below is a list of Monticello IL zip codes. For your research we have also included Monticello Area Code, Time Zone, UTC and the local Piatt County FIPS Code. Each Monticello Illinois zip code has a center Longitude / Latitude point (the Monticello center is -88.573303222656 / 40.027801513672). For your convenience we have also indicated if that zip code in Monticello observes Daylight Savings time.