www.state.sd.us/state/executive/deca/cultural/histpres.htm
State Historic Preservation Office

www.historicproperties.com
Online marketplace for buyers/sellers of old buildings

www.preservationdirectory.com
A directory of services and resources for historic preservation

www.cr.nps.gov/nr/
National Register of Historic Places Travel Itineraries

www.nthp.org
National Trust for Historic Preservation

www.cr.nps.gov/abpp
American Battlefield Protection Program

www.achp.gov 
Advisory Council on Historic Preservation

www.cr.nps.gov/history/nhlpgm.html
National Historic Landmarks Initiative

www.cr.nps.gov/nr
National Register of Historic Places