County Offices (Information on all county offices in U.S).: http://www.countyoffice.org/

Texas Historical Commission:  https://www.thc.texas.gov/

Advisory Council on Historic Preservation:  http://www.achp.gov

National Park Service: http://www.nps.gov/

National Trust for Historic Preservation:  http://www.preservationnation.org/

Preservation Action:  http://www.preservationaction.org

Preservation Texas, Inc.: http://www.preservationtexas.org/

Texas State Historical Association: http://www.tshaonline.org/

Texas Association of Museums: http://www.texasmuseums.org/

Smithsonian: http://www.si.edu/

The Library of Congress - "Caring For Your Collection": http://www.loc.gov/preserv/careothr.html