Below is a list of Keystone SD zip codes. For your research we have also included Keystone Area Code, Time Zone, UTC and the local Pennington County FIPS Code. Each Keystone South Dakota zip code has a center Longitude / Latitude point (the Keystone center is -103.364 / 43.9436). For your convenience we have also indicated if that zip code in Keystone observes Daylight Savings time. For more information on Keystone South Dakota you will find helpful business links and searches.