Clay County Profile - US Census Bureau information and inter-active tiger map of the county. Clay County South Dakota GenWeb - Genealogy resources include 1870 Census, listings from the 1909 Gazetteer Publishing Co. business directory, and farm, military and cemetery records. Clay County, South Dakota - Government site with details of each department and contacts. Clay County Fair - Includes map of fairgrounds, schedules of events and 4-H shows, and photographs from previous years. Occurs during August in Vermillion, the county seat. Clay County Office of Emergency Management - Provides emergency plans, disaster preparedness guides, shelter information, news and events, and contact information. Clay County Sheriff - Provides road conditions, warrant list, department directory, and contact information.