This study exploits a unique set of satellite and other spatially explicit data to examine the role of three exogenous geographic factors in shaping and constraining urbanization: biophysical land suitability for agriculture, distance to major ports and terrain slope. The setting is China in the 1990's, the most expansive process of urban growth in history. Our empirical results suggest that these geographical factors explain nearly half of the variation in urbanization levels. However, controlling for long-run levels, we nd a weakly negative relationship between agricultural land suitability and urban expansion from 1990-2000, which is consistent with the theoretical expectations that rising opportunity costs a ect the development of fertile lands. We examine heterogeneity in the e ects of geography using interactions with province xed e ects and, even more exibly, with a localized regression technique (geographically weighted regression). Our results indicate that agricultural land suitability has opposing e ects in di erent regions, for example leading to increased urban expansion in the Pearl River Delta and restricting urban expansion along the northern coast. These results should caution scholars against assuming homogeneous e ects of physical geography across regions when doing empirical analysis of urban dynamics.