Development sociologists generally agree that states play a critical role in promoting, as well as in impeding, development. However, far less scholarly consensus exists on the precise historical processes that lead either to strong or to weak states. This paper investigates the factors that shape varied state capacities through a comparative-historical analysis of two similar countries with divergent development outcomes—Trinidad and Tobago and Gabon. In the 1960s, both countries had comparably large amounts of oil wealth, minimal state involvement in the economy, and low levels of development. In the 1970s, state capacity in Trinidad and Tobago dramatically increased and the country went on to achieve high levels of development. The Gabonese state, on the other hand, remained weak resulting in persistent low levels of development. This paper traces the divergence in state capacity to variations in working class mobilization, specifically the particular type of working class movements in each country and the political opportunity contexts. In doing so, this paper reveals new agents and contingencies producing state capacity that are not predominantly discussed in the contemporary development literature, and the meso-level mechanics by which these agents are successful or constrained in doing so.