Found, been re-reading Michael Wallis's "Lincoln Highway" book, the one I referred to, which is not a mile by mile guide.
In many places, particularly east of the Rockies, there was a 1914-18 route, and a later route from the 30's that redefined the Lincoln Highway to follow U.S. numbered highways, older route reverted to state or county maintenance, or abandoned entirely. Some of the Lincoln Highway signage was moved accordingly, before it became an obsolete designation. Restoration markers can thus be found on both original and post-1930 routes.
If you want to follow the Lincoln Highway, you must figure out what you mean when you say that, which Lincoln Highway, and find guidebooks or online resources that fit. Because I live near Route 66 and travel sections regularly, I have collected resources for that. My Lincoln Highway book was a recent gift, have not yet put much into researching a trip, beyond recognizing that I've been regularly following old and new sections across northern Indiana, and between Chicago and Clinton.