You find it all over the US roads, at least those I have been riding so far:
And it was some kind of a mystery for the French that I am. Sure, today between Idaho Falls and Arco, there was just a long lonely highway of 66 mi (106 km), bushes and three 'buttes' as they are called.
And it's not this so called "lost river" that could help the highway feel a little less lonely. Anyhow, the Idaho Transportation Department has developed a volunteer program for groups or organisations to 'adopt' a 2 mile section of highway. By 'adopting' it is meant that the volunteers will clean their corresponding section of highway; and get their name on a sign.
All kinds of organizations adopt it to serve their community: churches, boy scouts, employees of a company, individuals... You can also decide to pay a company that will do it for you... but "c'est pas du jeu!"