It's like the pony express, except the library version. 

Sources:

https://en.wikipedia.org/wiki/Pack_Horse_Library_Project#:~:text=The%20Pack%20Horse%20Library%20Project%20was%20headed%20by%20Ellen%20Woodward,individual%20homes%20and%20to%20schoolhouses.

https://www.smithsonianmag.com/history/horse-riding-librarians-were-great-depression-bookmobiles-180963786/

Music: purple-planet.com