It’s arguable that we may very well be living though another one right now. But clearly the last great historical inflection point came exactly fifty years ago, and reached its apogee in the year of 1968. Lyndon Johnson was President, and a series of events led us to believe like Yeats, “that the center cannot hold, and that mere anarchy was loose upon the land.”
The Tet Offensive, MLK and RFK assassinations, the Praque Spring, racial conflicts, the Democratic Convention in Chicago, Lyndon Johnson's decision not to seek reelection and the election of Richard Nixon and Spiro Agnew, made 1968 quite a year.
Lyndon Johnson presided over it all and that's the story that historian Kyle Longley tells in LBJ's 1968: Power, Politics, and the Presidency in America's Year of Upheaval
My WhoWhatWhy conversation with Kyle Longley: