Deerfield, South DakotaDeerfield is an unincorporated community in Pennington County, in the U.S. state of South Dakota.HistoryA post office called Deerfield was established in 1892, and remained in operation until 1954. The community was so named on account of the area being a favorite hunting ground for deer.ClimateBlind Park is a SNOTEL weather station 7.8 miles northwest of Deerfield, at an altitude of 6890 ft.