It is no coincidence that the peak of the bookmobile era was also the golden age of small presses.
Detroit Public Library Archives
"The mobile library of the period played a crucial role in encouraging widespread reading, in supporting and improving access to education and in shaping local communities. It encouraged library use through its informality: As Eleanor Frances Brown wrote in her pioneering 1967 study of mobile libraries, 'There [was] no austerity or speaking in hushed voices' in the familiar bookmobile. In its approach and reach, the bookmobile, then offered an important alternative to the established cultural institutions not limited to big cities and state capitals, and was shaped, in no small part, by grassroots efforts of local communities that it later came to serve. As such, it inadvertently introduced another way of thinking about ways in which printed matter and information can travel and opened up novel possibilities for mobilizing also among countercultural and underground publishing communities prominent at the time; a model which these communities readily adopted."
Article: Here Comes the Small Press