Smithwick, South DakotaSmithwick is an unincorporated community and census-designated place in Fall River County, South Dakota, United States. The population was 39 at the 2020 census. Smithwick has been assigned the ZIP code of 57782.HistoryA post office called Smithwicks was established in 1887, and in 1901 the name was changed to Smithwick. Smithwick was named for a railroad engineer.EducationThe school district for almost all of Smithwick is Oelrichs School District 23-3. A small piece is in Hot Springs School District 23-2.