Below is a list of Keystone IA zip codes. For your research we have also included Keystone Area Code, Time Zone, UTC and the local Benton County FIPS Code. Each Keystone Iowa zip code has a center Longitude / Latitude point (the Keystone center is -92.202102661133 / 42.000499725342). For your convenience we have also indicated if that zip code in Keystone observes Daylight Savings time.