Under the First Amendment, the U.S. government cannot outright ban literature in the United States, but as Mark Crispin Miller, author and professor of media studies at New York University, explained, books can be hidden from public view or written off as conspiracy theory in order to prevent people from reading them.

While censorship is often conducted by corporations and governments to prevent words, images or ideas from entering the mainstream, censorship of literature has been around as early as 399 B.C. and has affected intellectuals and philosophers such as Socrates.

Currently, materials most likely to be censored contain sexually explicit content, offensive language, unsuitable material for children, gay themes, objectionable religious views, nudity, racism and sexual education, according to the American Library Association.

According to the American Civil Liberties Union, “The urge to censor is hardly the monopoly of any political group. But the greatest threat today comes from the fundamentalist right, with its ideological hostility to other religious or philosophical systems, to homosexuality, to sex education, and indeed to the basic idea of secular education.”

In order to bring awareness to the issue of censorship in the U.S., the American Library Association hosts an annual Banned Books Week. It encourages libraries, schools and bookstores to draw attention to the harms that can occur to society and individual freedoms if books are censored.

“Whether in print or digital format, books are a precious resource, providing us with information, entertainment, opinions, ideas, and a window on lives far different from our own,” wrote Molly Raphael, president of the American Library Association, in a piece to remind Americans that censorship still exists, even with the existence of the Internet.

“Free access to books and ideas is the foundation of our government and our society, enabling every person to become an educated participant in our democratic republic.”

Between 2000 and 2009, there were 5,099 challenges reported to or recorded by the Office for Intellectual Freedom. In 2012, there were 464 challenges, marking a 25 percent increase from 2011, but still low compared to the number of challenges seen in the 1980s and 1990s — especially considering the Office for Intellectual Freedom simplified the process of challenging books. In 2013, there were 307 challenges, including to the books “The Hunger Games” and “Fifty Shades of Grey.”

Since some books that are challenged end up disappearing from libraries and bookstore shelves, the Forbidden Bookshelf is working to restore Americans’ access to censored literature by making these pieces available in an e-book format.

Forbidden Bookshelf recently shared five books it will re-release to the public, which inspired MintPress News to find five other pieces of literature that contain material so controversial that they have had to be removed from libraries and classrooms.

1. The Adventures of Huckleberry Finn, Mark Twain, 1884

One of the most frequently challenged books in the U.S. is Mark Twain’s “The Adventures of Huckleberry Finn.” It was first banned in Concord, Massachusetts, in 1885, as it was viewed as “trash and suitable only for the slums.” While some see the book as historically and culturally important, it is still challenged and banned in some parts of the U.S. because of its frequent use of racial slurs. Although such disparaging language was part of the everyday vocabulary when Twain wrote the novel, many argue that the book should be banned because it is “racially insensitive,” “oppressive” and “perpetuates racism” against blacks, Native Americans and poor white Americans.

2. Gone With the Wind, Margaret Mitchell, 1936

Its reputation as one of the best-selling novels of all time hasn’t stopped efforts to censor the Pulitzer Prize-winning story of the spoiled daughter of a Southern plantation owner before, during and after the Civil War. While the book has been praised for its criticism of the South’s positive outlooks on slavery and racist attitudes, Mitchell’s inclusion of words like “damn” and “whore” has also given as reasons why the book should no longer be available to the public.

3. The Jungle, Upton Sinclair, 1906

Despite being credited with leading to the creation of the Food and Drug Administration and meat inspections, Sinclair’s story — first published in serial form in a socialist newspaper — was initially classified as a dangerous, socialist text. Though Sinclair’s story was never officially banned in the U.S. and, in fact, has been used to teach generations of American students about muckraking and yellow journalism in social studies classes, publishers have been accused of changing the text to appease corporations.

4. Our Bodies, Ourselves, Boston Women’s Health Book Collective, 1971

Fictional tales aren’t the only ones that are challenged and subject to censorship, which is evident by the attempts during the 1970s to ban a text about female anatomy and sexuality. One public library that opted to remove the book from its collection said the book “promotes homosexuality and perversion” — since the word “vagina” remains taboo in the U.S., few are surprised about motions to keep this book off shelves.

5. Sexual Behavior in the Human Male, Alfred C. Kinsey, 1948

The number one reason a book is censored is because of sexual content. For this reason, it should come as no surprise that a survey in which men and women were questioned about their sex lives didn’t receive a warm welcome. Though Alfred Kinsey’s survey was the first of its kind, it remains a controversial text even today.