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

Contours from US Topo products are in development as a nationwide service for viewing at large scales from 36K to 18K. US Topo contours were initially made available for download as of February 2013 as staged data in Esri File Geodatabase (FGDB) 10.1 format and pre-packaged in 1x1 degree tiles. In February 2014, staged contours also became available in additional formats of either FGDB 9.3.1 or Shapefile besides FGDB 10.1.