The county is entirely within the Pine Ridge Indian Reservation and contains part of Badlands National Park. The county's median household income makes it the forty-eighth poorest county in the United States. (Kalawao County, Hawaii, is the poorest .)
In recent years, its residents have become more politically active, voting in state and national elections. A voter registration drive in 2002 helped gain support for the Democratic candidate for the US Senate, and turnout in Shannon County and across the Pine Ridge Indian Reservation helped narrowly elect Tim Johnson to office. The county has the distinction of having the highest percentage of Democratic votes for President in the 2004 election of any county in the US (85%), in 2008 with 88.69%, and in 2012 with 93.39%. It is an alcohol prohibition or dry county, the only such county in South Dakota; taxes on alcohol illegally consumed within the county go to other counties.
Shannon County is one of two counties in South Dakota that does not have its own county seat (Todd County is the other). Hot Springs in neighboring Fall River County serves as its administrative center. It is also one of five South Dakota counties that are entirely on an Indian reservation. (The others are Corson, Dewey, Todd, and Ziebach.)
Until 1982 Shannon and Washabaugh County, South Dakota, were the last unorganized counties in the United States. Although it was organized and received a home rule charter that year, Shannon, as noted above, contracts with Fall River County for its Auditor, Treasurer, and Registrar of Deeds.
Note: Created before 1880; included with Pine Ridge Indian Reservation in 1890-1910; reported in 1920-90.