Where are large scale contours for viewing and download as shown in US Topo products?

Large scale contours from US Topo products are included in an ArcGIS REST service endpoint or WMS for viewing at scales of 50K and larger. US Topo contours are available for download in The National Map Download Client as staged data that has been pre-packaged in 1x1 degree tiles in Esri File Geodatabase 10.1 or Shapefile format.