"The United States today, according to most studies, is among the least corrupt nations in the world. But America's past was checkered with political scandal and widespread corruption that would not seem unusual compared with the most corrupt developing nation today. We construct a "corruption and fraud index" using word counts from a large number of newspapers for 1815 to 1975, supplemented with other historical facts. The index reveals that America experienced a substantial decrease in corruption from 1870 to 1920, particularly from the late-1870s to the mid-1880s and again in the 1910s. At its peak in the 1870s the "corruption and fraud index" is about five times its level from the end of the Progressive Era to the 1970s. If the United States was once considerably more corrupt than it is today, then America's history should offer lessons about how to reduce corruption. How did America become a less corrupt polity, economy, and society? We review the findings and insights from a series of essays for a conference volume, Corruption and Reform: Lessons from America's History, for which this paper is the introduction that attempt to understand the remarkable evolution of corruption and reform in U.S. history"--National Bureau of Economic Research web site.