Racial segregation in the United States, as a general term, included the segregation or “hypersegregation” of facilities, services, and opportunities such as housing, medical care, education, employment, and transportation along racial lines. The expression most often refers to the legally or socially enforced separation of African Americans from other races, but also applies to the general discrimination against people of color by white communities. As well as the physical separation and provision of separate facilities (especially during the Jim Crow era), the term can also refer to other manifestations of racial discrimination, such as separation of roles within an institution: for example, in the United States Armed Forces before the 1950s, black units were typically separated from white units but were led by white officers. De jure segregation, sanctioned or enforced by force of law, was stopped in the United States by federal enforcement of a series of Supreme Court decisions after Brown v. Board of Education in 1954. Its elimination lasted through much of the 1950s, 1960s, and 1970s, while civil rights demonstrations resulted in public opinion turning against enforced segregation. De facto segregation — segregation “in fact”, without sanction of law — persists in varying degrees to the present day. The contemporary racial segregation seen in the United States in residential neighborhoods has been shaped by public policies, mortgage discrimination, and redlining, among other factors. Hypersegregation is a form of racial segregation that consists of the geographical grouping of racial groups. Most often, this occurs in cities where the residents of the inner city are African Americans and the suburbs surrounding this inner core are often white European American residents. The idea of hypersegregation gained credibility in 1989 due to the work of Douglas Massey and Nancy A. Denton and their studies of “American Apartheid” when whites created the black ghetto during the first half of the 20th century in order to isolate growing urban black populations by segregation among inner-city African-Americans.