This paper, using mostly data drawn from a study of the criminal work of the Superior Court of Alameda County, California, from 1880 on, explores the history of plea bargaining. Plea bargaining, it turns out, was used in Alameda County from at least 1880, though it was by no means as common in the late 19th century as it is today. There is also ample evidence of "implicit plea bargaining," that ... [Show full abstract] is, pleading guilty in expectation of a lighter sentence. The data from this study suggest that plea bargaining cannot be explained simply as a reaction to crowded court conditions. It is connected with structural and social changes in criminal justice, in particular, the rise of professional police and prosecutors.