To Morison, American liberalism was invented by his ancestors, the descendants of the Puritans. As he made clear in his Oxford History, rudimentary versions of most American progressive movements, including civil rights for blacks, feminism, and the rudiments of the ideology of environmentalism (Thoreau's Walden), were up and running in the greater Boston area by the 1840s.
In other words, American liberalism was invented by the oldest and most socially respectable hereditary elite in the country's least ethnically diverse region, and imposed from the top down.
In other words, it was the WASPs and not the Jews who invented the left-wing ideas that are currently turning the United States into a Third World country. Thanks for nothing you Anglo-Saxon morons!