We examine the economic and political determinants of decisions taken by local governments regarding the amount of new land to be assigned for development. The analysis draws on a massive database, which includes more than 2,000 Spanish municipalities during the 1999-2003 term-of-office. The increase in developable land in this period is explained using a wide set of variables that capture the specific traits of each municipality in 1999. The variables were selected following a review of recommendations made in the literature on urban growth controls and by taking into account other factors that might be considered specific to Spain. Our results show that urban expansion is influenced by a variety of factors. Thus, the communities found to be expanding most: (i) are rich, (ii) have more new housing purchasers, (iii) are in a weak financial position, (iv) are controlled by parties to the right of the political spectrum, (v) have a low electoral turnout and local government bodies that do not face serious electoral competition, and (vi) have more land but a lower proportion of environmentally valuable land.