A political movement rallies against underregulated banks, widening gaps in wealth, and gridlocked governments. Sound familiar? More than a century before Occupy Wall Street, the People's Party of the 1890s was organizing for change. They were the original source of the term "populism," and a catalyst for the later Progressive Era and New Deal. Historians wrote approvingly of the Populists up into the 1950s. But with time and new voices, led by historian...