Municipal incorporation can have profound impacts on the urban and political geography of the regions in which they incorporate. These impacts and declines in the rate of municipal formation lead to the question of why municipalities incorporate. The authors synthesize an overview and analysis of the historical literature with a media literature review to construct a comprehensive classification system of theories that explain municipal incorporations. Twelve new micromotives such as eligibility for government grants and economic development are identified. Moreover, the review surprisingly reveals that spatial motives, in contrast to service motives, play the largest role in new municipal incorporations.