要旨：When do we have a company town and when do we have a multi-firm city? The objective of this paper is to analyze the impact of public infrastructure investment decisions, in a decentralized urban system, on types of cities. This is done in a one sector spatial general equilibrium model of a closed economy. The reason for investment in public infrastructure is that it would lead to a reduction in the fixed costs of production by all firms in the industry within the city. As a result of that multi-firm cities are formed. This approach models localization economies explicitly instead of assuming that multi-firm cities are formed due to the enhanced productivity resulting from the increase in the size of an industry in a given city. On the other hand, when infrastructure is not provided, then a company town will be formed by a developer because of the fixed cost required by each firm. The decision to invest in the provision of public infrastructure or not depends on which type of city will provide households with higher utility. This paper characterizes the conditions that leads to each of the two equilibrium configurations and presents some comparative static results.