This database for the Oregon, California, Mormon Pioneer, and Pony Express National Historic Trails is comprised of digital topographic data and reference line established using point data gathered with Global Positioning System (GPS) technology which represents only an approximation of the centerline of the trails system. This database, which is to be used in conjunction with ArcView software, is provided to assist the user in analyzing the visibility of any proposed location within 5 miles of the GPS reference line of the trails in order to evaluate effects to the landscape and setting of National Historic Trails in accordance with the National Historic Preservation Act and its implementing regulations at 36CFR Part 800. This data imparts no information relative to land ownership and conveys no right of access to any land. Legal access to or across private land requires permission of the landowner.