Improving our understanding of the economic past ultimately rests on refreshing the stock of economic facts. The present volume contributes new observations of crop yields and cropping systems in Northern France, the Low Countries, and England, quarried from documentary deposits laid down during the half-millennium preceding the Industrial Revolution. Because yields and crop rotations are strongly affected by local factors, the fruits of this enterprise resist easy summary. Even so, a few broad patterns suggest themselves. The first is the absence of any movement in the upper tail of the distribution of cereal yields that might indicate a fundamental revolution in agricultural technology before the nineteenth century; the true revolution in crop yields dates to the massive application of commercial fertilizers in the closing decades of the nineteenth century. The second is the persistence of wide spatial variation in yields. The data do not permit the computation of national mean yields, but the general impression is one of slow movement, especially after 1650 when yields commenced a gradual and unbroken rise into the nineteenth century. The last general impression is one of a U-shaped time path in the highest yields, which declined for varying lengths of time after the Black Death before recovering in the sixteenth, and in some cases the eighteenth century. If this pattern continues to show up in the data, it should be granted the status of a stylized fact to be explained.