There are some obvious similarities between the Yellowstone Trail Association and the Lincoln Highway Association. They were born within a year of each other and they both promoted coast to coast routes for the up and coming automobile. But there are some very significant differences as well. The LHA was thinking coast to coast from the beginning. At first, J. W. Parmley and friends just wanted a decent road to Aberdeen, SD, from their homes in Ipswich. Once the group got going, the goal quickly extended to other South Dakota towns. Before long they set their sights on the nation's first federally protected national park and named their group after it. But there were even bigger needs and the group seems to have adopted the "a good road from Plymouth Rock to Puget Sound" slogan even before the association officially formed in October of 1912.
The United States is not smoothly tapered but it is clearly wider at its northern edge than at its south. A straight line from Savannah to San Diego is about 2000 miles long. A similar line between Boston and Seattle is just about 3000 miles. The path that the Yellowstone Trail eventually followed covered about 3600 miles in connecting Plymouth Rock with Puget Sound. Planning a couple hundred miles per day on a historic road is not overly conservative so this approaches three weeks for a one way pass plus staging and return. It's going to be awhile before I undertake this.