Existing research establishes that political trust is not only an important determinant of individual political behavior and government effectiveness, but may also measure the health of civic society. This article presents evidence that assimilation is corrosive of political trust, focusing specifically on the incorporation of Latinos in Chicago. Various strands of assimilation theory predict that as Mexicans naturalize and join the electorate, and as Puerto Ricans migrate to the mainland, they will be increasingly cynical about politics. This theory is tested with data from a recent survey of the Latino population in Chicago. Mexican American citizens are found to be less trusting of government, while Mexican-descent non-citizens remain more idealistic. Puerto Ricans born on the island of Puerto Rico are found to be more trusting than are Puerto Ricans born in the United States.