According to the First Amendment Encyclopedia

"Book banning is the most widespread form of censorship in the United States, with children’s literature being the primary target. Advocates for banning a book or certain books fear that children will be swayed by its contents, which they regard as potentially dangerous. They commonly fear that these publications will present ideas, raise questions, and incite critical inquiry among children that parents, political groups, or religious organizations are not ready to address or that they find inappropriate.”  Source: First Amendment Encyclopedia

Intellectual Freedom

The American Library Association (ALA) champions intellectual freedom which is defined by the ALA as “the right of every individual to seek and receive information from all points of view without restriction." Source: ALA Intellectual Freedom and Censorship Q&A

Challenges & Bans

The American Library Association tracks challenges to library materials every year. Challenged books are defined by the ALA as “an attempt to remove or restrict materials, based upon the objections of a person or group” while banning is defined as the removal of those materials.

This infographic produced by the American Library Association details library materials affected by censorship attempts in America in 2019.

Censorship by the Numbers (and other ALA infographics)