Studies comparing regional income in Japan before and after World War II have frequently drawn a picture of radical change from an economy characterized by large regional disparities to one characterized by small regional disparities. This paper comes to a very different conclusion. Based on estimates of prefecture-level value added for five benchmark years from 1890 to 1940 (a detailed description of our estimation methodology is provided), we examine trends in the gap of economic development between prefectures during the pre-war period and find that this gap was much smaller than claimed in preceding studies and, in fact, not much greater than during the post-war period. Observing, moreover, a decline in inter-prefectural differences in terms of per-capita gross value added during the pre-war period, we conduct a factor analysis and find that a major reason for this decline was a decline in inter-prefectural differences in same-industry labor productivity. Thus, the picture of modern Japan's economic development presented here is very different from the one painted by preceding studies.