US Topo

The accuracy statement printed in the margin of most 20th-century USGS topographic maps referred to absolute horizontal and vertical accuracy.
Historical USGS topographic maps included spot elevation labels on mountain peaks and local high points.
US Topo is intended to serve map users who are not GIS specialists.
Except for the following three cases, US Topo maps have no copyright:
Publication of 1:25,000-scale US Topo maps in Alaska began in July 2013.
Not for US Topo maps. These maps are derived from GIS data and packaged in traditional map form for the benefit of non-specialist users. Most of the data used to make US Topo maps are available from USGS through map services and staged datasets.
GeoPDF is a TerraGo Technologies published extension to the Adobe PDF file format. GeoPDF is not a separate format; any GeoPDF conforms to the base PDF specification, and GeoPDF files can be used as plain PDF files. More information:
Most GIS vendors do not yet provide geospatial PDF import capabilities. US Topo maps are derived from GIS data sets and are formatted as PDF for the benefit of non-specialist users.
GeoMark is TerraGo's geospatial data extension to PDF markup.
US Topo production follows the U.S. Department of Agriculture National Agricultural Imagery Program (NAIP). USGS intends to refresh the map series for the conterminous United States every 3 years.