G'day brucemarshall56,
...the National Map Viewer is certainly still the best option for obtaining US DEM data and the only one I use for that purpose. There is a brief 'account' of how to obtain the data from this resource in the Help file for TransDEM (press the [F1] key) under the heading "
Terrestrial and other DEMs" and the sub-heading "
NED" but a dedicated tutorial covering this aspect seems to be missing from the otherwise comprehensive "instructions"...
...that notwithstanding, there are detailed instructions on how to use the service if you click on the "download" link in the text of the TNM main page, at this link...
TNM download instructions...which should give you a good idea of how to proceed...
Jerker {:)}