From charlesreid1

An example of how to hook up Leaflet to use the USGS National Maps tile set.

http://viewer.nationalmap.gov/example/maps/Leaflet_Example.html

An example of how to make a topographical map:

http://viewer.nationalmap.gov/example/maps/pqs_profile.html

The above example uses a tile set to render contours (contours are represented as images), whereas the D3 Map project I'm working on uses a shapefile containing detailed contours represented as polygons (and therefore much slower).