Ken & Marcia Powers are credited with being the first people to continuously thru-hike the ADT (as per the ADT website). The went westbound, from the Atlantic Ocean at Cape Henlopen SP to the Pacific Ocean Pt Reyes National Seashore, and appear to have take the southern route through the country's mid-section (perhaps the only established route at the time?)
Marcia Powers made the following note on their route: "Follow the American Discovery Trail as published in their 2005 guide know as TBT using first established route through Dark Canyon, UT (changed after first exploration of route)." The pair took only 4 "zero" days during their nearly 8-month hike.
The Powers' trail journal is here: http://www.trailjournals.com/GottaWalkADT/
Many articles on the hike are available on the web.