Abstract: We provide a theoretical model linking limits to the observability of soil quality to state rulers’ ability to tax agricultural output, which leads to a higher political fragmentation. We introduce a spatial measure to quantify state planners’ observability in an agricultural society. The model is applied to spatial variation in the 1378 Holy Roman Empire, the area with the highest political fragmentation in European history. We find that differences in the observability of agricultural output explain the size and capacity of states as well as the emergence and longevity of city states. Grid cells with higher observability of agricultural output intersect with a significantly lower number of territories within them. Our results highlight the role of agriculture and geography, for size, political, and economic organization of states. This sheds light on early, though persistent, determinants of industrial development within Germany, and also within Central Europe.