The IMLS Public Library Survey is the most comprehensive source of data about US libraries. This video provides an introduction to the result data and associated documentation.
With the news this week that the Trump Administration is trying to destroy the Institute for Museum and Library Services - for the third year in a row - library advocates across the United States snapped into action. ALA fired up a "send an email to your representative" tool as well as an interactive table for looking up your representative's and senator's respective votes on past library funding bills. As BookRiot says, not hyperbolically: "[d]efunding the IMLS would effectively end all federal funding of public libraries."