Most of the United States' judicial work takes place in the country's state trial courts. These tribunals preside over everything from traffic tickets to murder trials, from routine debt collection to massive environmental torts. Given their expansive role, the manner in which these courts function is of immense significance. But ultimately, we know very little about these institutions. Our ignorance flows both from trivial bureaucratic turf battles and from deeply rooted principles of local government, a phenomenon I have called “data federalism.” In the last few decades, we have begun to form a partial image of the activities of these organs of government; but we know almost nothing about their past, and the little we do know suggests the dangers of extrapolation. This essay explores the extent of our ignorance of state trial courts and the difficulties of overcoming it.