Lawrence Goodwyn’s book restored the Populist movement to its place as one of the country’s most important radical moments, after generations of historians had dismissed it as little more than an irrational rural outburst.

A half-century after its publication, Ira Kipnis’s The American Socialist Movement is still the best guide to the politics of the Socialist Party. Though it unfortunately stops its narrative in 1912, it’s a great exploration of the debates that shaped the party.

While dated and marred by Draper’s undisguised hostility to the CP, this is still the definitive account of the rise of American communism, from its origins in the 1910s through the 1920s.