The twenty-first century “patent litigation explosion” is not unprecedented. In fact, the nineteenth century saw an even bigger surge of patent cases. During that era, the most prolific patent enforcers brought hundreds or even thousands of suits, dwarfing the efforts of today’s leading “trolls.” In 1850, New York City and Philadelphia alone had ten times more patent litigation, per U.S. patent in force, than the entire United States in 2013. Even the absolute quantity of late-nineteenth-century patent cases bears comparison to the numbers filed in recent years: the Southern District of New York in 1880 would have ranked third on the list of districts with the most patent infringement suits filed in 2014 and would have headed the list as recently as 2010.
This Article reveals the forgotten history of the first patent litigation explosion. It first describes the rise of large-scale patent enforcement in the middle of the nineteenth century. It then draws on new data from the archives of two leading federal courts to trace the development of patent litigation from 1840 to 1910 and to outline the scale, composition, and leading causes of the litigation boom. Finally, the Article explores the consequences of this phenomenon for the law and politics of the patent system. The effects of the litigation explosion were profound. The rise of large-scale patent assertion provides a new explanation for patent law’s crucial shift from common law to equity decision making in the middle of the nineteenth century. And at its height, the litigation explosion produced a political backlash that threatened to sweep away the patent system as we know it. Recovering the history of patent law during this formative and turbulent era offers fresh perspectives on the patent reform debates of today.