The document discusses the popularity of the book "Black Elk Speaks" in the 1960s and 1970s. It was republished in 1961 and gained popularity throughout that decade. Vine Deloria Jr. wrote an introduction to the 1979 edition discussing the book's importance and references cultural trends of the era. His grandson Philip J. Deloria also wrote an introduction reflecting how the book resonated with the mood of the time. The Delorias explain how the book would have found audiences during this time period by speaking to themes of environmentalism, rebellion against authority, and rapid technological change.