For many decades, communities in the United States have been troubled by criminal activities, including serious violent crimes, committed by youth gangs. The prevalence and seriousness of gang problems have fluctuated over time, with gang activity escalating during some periods and diminishing during others. The last three decades of the 20th century were characterized by a major escalation of youth gang problems throughout the Nation, accompanied by a substantial increase in gang studies, surveys, and reports. These reports conveyed a general impression that the number of localities experiencing gang problems had increased but failed to provide concrete, national-level information on the size of the increase, the localities involved, and their location. This information gap is filled by the present Report, which presents detailed information on the numbers and specific identities of gang problem localities, the size of these localities, rates of growth, and location by State and region of the cities, towns, villages, and counties that reported gang problems between the 1970's and late 1990's. Trend and rate analyses over a three-decade period were made possible by the availability of baseline data collected by the first national youth gang survey, conducted during the 1970's. Major findings of the Report are summarized below.

The number of localities reporting gang problems increased dramatically between the 1970's and 1990's. By the late 1990's, 3,700 identified localities in the United States—about 2,550 cities, towns, and villages and 1,150 counties, totaling the highest number ever reported—had reported the presence of gang problems. These figures represent a nearly tenfold increase in the number of cities and an elevenfold increase in the number of counties reporting gang problems during the study period.

In the 1970's, 19 States reported gang problems; by the late 1990's, all 50 States and the District of Columbia had reported gang problems. In the 1970's, the combined population of all cities reporting gang problems was about 25 percent of the population of all cities, and the population of all counties reporting gang problems was about 40 percent of the all-county population. By the late 1990's, the population of gang cities had risen to about 60 percent of all cities, and the gang-county population had risen to about 90 percent of the all-county population.

The States with the largest number of gang-problem cities in 1998 were California (363), Illinois (261), Texas (156), Florida (125), and Ohio (86). Of these, only two, California and Illinois, reported large numbers of cities with gang problems in the 1970's. The States with the largest number of gang counties in 1998 were Texas (82), Georgia (61), California (50), Illinois (42), and Florida (40), in that order; the South replaced the Northeast as the region with the most top-ranking States.

Nationwide, there was a substantial decrease in the concentration of gang cities in the higher ranking States as gang problems continued to spread to new States. In the 1970's, the top four States contained about three-quarters of all gang cities; in the 1990's, the percentage had fallen to about one-third. In the 1970's, only 8 States reported 5 or more gang cities; in the 1990's, all 50 States reported 5 or more. In the 1970's, gang counties were concentrated in a relatively small number of States, principally California and Texas. By the 1990's, gang counties were spread widely throughout the Nation. In the 1970's, only 6 States reported more than 5 gang counties; in 1998, 47 States reported more than 5. In 1998, gang-problem cities were concentrated in a relatively small group of counties, with the top-ranking, high-concentration counties containing more than 40 percent of all gang cities. Cook County, IL, reported the largest number of gang cities, followed by Los Angeles County, CA. Riverside and Orange Counties in California also reported high concentrations of gang cities.

The regional location of gang cities changed radically during the three-decade period. In the 1970's, the West ranked highest in the reported number of gang cities, and the South ranked lowest. By 1998, the South ranked second, with a 33-fold increase in gang cities since the 1970's. Traditionally, gang problems have been a big-city phenomenon, and this situation continued during the three decades prior to 2000. In the late 1990's, there were approximately 200 cities with populations of 100,000 or more, and every one of these large cities reported youth gang problems. Comparison of the numbers and percentages of gang cities in designated population categories in 1998 with the numbers and percentages of all U.S. cities shows that gang cities with more than 25,000 inhabitants (larger gang cities) made up 43 percent of all gang cities but contained 88 percent of their population. These larger gang cities made up 77 percent of the number of all larger cities, but 86 percent of their population, and 3 percent of the number of all U.S. cities, but 52 percent of their population.

Gang problems, however, were by no means confined to large cities. One of the best documented developments of this period was a striking increase in the growth of gang problems in the Nation's smaller cities, towns, and villages. The size of the average gang city population fell from 182,000 to 34,000, an 81-percent decline. The number of gang cities with populations less than 25,000 rose from 35 percent of all gang cities to 57 percent, and the population of gang cities smaller than 25,000 rose from less than 1 percent of the total U.S. city population to about 7 percent. The number of gang cities with 1,000 to 5,000 inhabitants increased more than 27 times, and the number of gang cities with 5,000 to 10,000 inhabitants increased more than 32 times.

Reasons for the striking increase in the number of gang-problem localities are discussed in this Report under seven headings: drugs, immigration, gang names and alliances, migration, government policies, female-headed households, and gang subculture and the media.

An analysis of projected growth rates of gang-problem cities provides a basis for predicting future trends in the number of gang cities. The data provide considerable support for a prediction that the rate of growth that prevailed during the later 1990's will decrease in the early 2000's and some support for a prediction that the actual number of gang localities in the United States will decrease.