Discussions of violence often distinguish between two different dimensions: personal crimes and group violence. The first includes such activities as murder, molestation, robbery rape and assault, while the latter refers to riots, gang warfare, conflicts between labor movements and the police, lynchings, terrorism and political uprisings. Although this is a plausible method of classification, there are violent acts not easily placed into one category or another; for example the Kennedy assassination (1963) or the mass suicide at Jonestown. Moreover, there is frequently a complex interplay between these two dimensions that increases the difficulty of making clear-cut divisions.

The overall rate of personal crime reached a century low period in the mid-1950s and then began a relatively steady climb, peaking in the 1980s and then beginning a steady downward trend for most of the 1990s. Despite the fluctuations throughout this period a number of patterns emerge. Assaults and killings were typically done by young men against other men of similar age and race with whom they were acquainted; rapes and fatal incidents of domestic violence were overwhelmingly committed by men against women; assaults, most homicides and suicides involved the use of a gun; and both offenders and victims of violent crime have been disproportionately black.

The United States had roughly similar crime rates when compared with the other Western nations, but significantly higher levels of lethal violence. There was no shortage of theories as to why it was so or how to resolve it. Several researchers argued that as long as there were significant levels of poverty income inequality and racial segregation, the United States would continue to have high levels of violence. Some argued that strengthening positive cultural institutions, such as marriage and the two-parent family, and attacking negative social practices, such as drug use among the young, would decrease the propensity for individuals to engage in violent crime. Others contended that more effective crimefighting techniques such as community-based policing, along with sentencing reform, and an increase in prisons would discourage the relatively small subset of the population responsible for most violent crimes. Perhaps the most frequently cited difference between the United States and the other Western nations was the powerful role guns play in American culture. While almost all researchers agreed that guns constituted one of the critical contributing causes in explaining the country’s uniquely high levels of violence, there was only intermittent and minimal political action regarding the topic.

Group violence in post-Second World War America followed a slightly different pattern. Labor violence which had been a significant issue in the 1930s generally vanished, although there were some notable exceptions (e.g. the national strike of independent truckers in 1974). Far and away the most intense and widespread source of group conflict centered on the issue of race. The Civil Rights movement, which began to make inroads in the 1950s, was constantly met with verbal harassment, beatings, cross burnings, lynchings, bombings and assassinations. Leaders of the movement capitalized on these reactions by deliberately going into dangerous areas of the South where their presence would frequently lead to savage reactions by the local police and citizens. The media images of peaceful protesters being attacked by fire hoses and police dogs helped galvanize the country and its political leaders to support them in their goal of racial desegregation.

As the gains of the civil-rights movement only partially translated into improvements for African Americans, there began in the mid-1960s a series of riots in almost every major northern city with a sizeable black population. These riots resulted in millions of dollars of damage, the destruction of entire neighborhoods and the deaths of nearly 250 people, most of whom were shot by police or National Guardsmen. By the early 1970s this trend slowed down, but throughout the 1980s and 1990s there were major riots in Miami, FL (1982, 1984, 1987), Philadelphia, PA (1985) and Los Angeles, CA (1965, 1992). Most of these riots involved African Americans or Latinos, and were sparked by incidents involving police and the arrest of a minority suspect.

Political debates about the causes of violence and about how best to prevent it played a significant role in several elections, one obvious example being the 1968 campaign in which both Richard Nixon and George Wallace cast themselves as law and order candidates. Throughout the 1980s a general consensus developed among policy-makers, although not necessarily among social scientists, that more aggressive measures were required to cope with the increasing levels of violence. As a result there was a boom in prison construction, hundreds of laws were added to federal and state criminal codes, increasing penalties and decreasing the discretionary power of the judiciary, the FBI was given increased authority to wiretap and infiltrate suspicious groups and there was a substantial increase in the use of the death penalty.

One prominent and ongoing feature of the debate about violence in America has been the role of the media. The quantity and graphic nature of violent images in most forms of media, especially those targeted at younger consumers, increased dramatically from the 1950s into the 1990s. The release of John Carpenter’s Halloween (1978) introduced a whole new genre of violent horror movies known as “slasher” films (e.g. Nïghtmare on Elm Street; Friday the 13th; Scream) in which several characters per film were brutally slaughtered in explicit detail. Many of the bestsellers of the 1980s and 1990s were by authors who frequently employed violent imagery in their work such as Stephen King, Clive Barker, and R.L. Stein. Supreme Court decisions in the late 1960s that struck down many censorship laws thereby increased availability of pornography, which then subsequently increased the amount of sexually violent material. Although television presented less graphic images than movies, it was frequently cited as a major cause of violence in society both because of the high number of violent crimes presented in news and entertainment shows and because of its enormous audience (see violence and media).

However, social-science researchers were unable effectively to demonstrate causal connections between violence in the media and actual incidents of violence. There were several studies associating extensive exposure of young males to violent television images with an increased probability of aggressive behavior, but even here there have been a number of challenges as to the strength of the evidence to support this claim.

Some researchers concluded that the most significant effect of violence in the media was the perception it created of criminals in American society and how this perception translated into increasingly violent and severe criminal-justice policies.