The counterculture of the 1960s refers to an anti-establishment cultural phenomenon that developed first in the United Kingdom (UK) and the United States (US) and then spread throughout much of the Western world between the early 1960s and the mid-1970s, with London, New York City, and San Francisco being hotbeds of early countercultural activity. The aggregate movement gained momentum as the American Civil Rights Movement continued to grow, and became revolutionary with the expansion of the US government's extensive military intervention in Vietnam. As the 1960s progressed, widespread social tensions also developed concerning other issues, and tended to flow along generational lines regarding human sexuality, women's rights, traditional modes of authority, experimentation with psychoactiv