Most societies have some kinds of sexually explicit words, images, and other materials that are disapproved, prohibited, illegal, or restricted in circulation; that are portrayed in a manner that is generally unacceptable; and that are classified as pornography. The term pornography often denotes subjective disapproval of materials rather than their content or effect.

Historically, attitudes toward pornography tend to be cyclical. The most recent expansion in the United States of the availability of such materials began in the 1960s, as a result of larger social trends, including the civil rights movement, the counterculture and antiwar movement, approval of the contraceptive pill, and liberal U.S. Supreme Court decisions providing access to previously banned novels and films. These trends contributed to continuing discussion on whether new forms of social control would be necessary to cope with pornography, and federal government investigations into pornography's impact were launched in 1968 and 1985.

Both...