It started when I was in high school, and some idiots wanted to ban The Adventures of Huckleberry Finn because of the language regarding "Negro Jim".
It's also partially due to reading Ray Bradbury's Fahrenheit 451.
Ironically, that book has been banned in some of the US ... because it mentions that even the Bible was eventually banned.
Usually, I read the book and find out it isn't as "evil" as the media (or organization wanting to ban it) says it is.
Here's a list of some books that have been banned in the US, in addition to the two above:
Catcher in the Rye
Where's Waldo
The Diary of a Young Girl (Anne Frank)
To Kill a Mockingbird
The Harry Potter series
Little Red Riding Hood
Sleeping Beauty
The Grapes of Wrath
Harriet the Spy
Uncle Tom's Cabin