要旨：I propose a model with multiple cities that allows inter-city interactions through costly trade, internal migrations, and firm relocation. The model features multiple sectors, heterogeneous firms, and heterogeneous workers. The comparative statics of the model focuses on three shocks: falling transport costs, declining education costs, and increasing high-skill intensities. I show that: (1) there is a non-monotonic relationship between transport costs and the spatial income inequality; (2) a structural transformation triggered by declining education costs reduces the inequality, (3) the one due to a skill-biased technological change, however, predicts the opposite. The theoretical predictions are confirmed by a panel regression using the data from 32 countries with 1,962 regions.