AbstractThis article sheds new light on how conservatism has affected American state development by tracing the history of how block-granting transformed from a bipartisan tool to solve problems of public administration in the 1940s into a mechanism to roll back and decentralize the welfare state that had reached its zenith in the 1960s. By the early 1980s, conservative policymakers had coopted the previously bipartisan tool in their efforts to chip away at the increasingly centralized social welfare system that emerged out of the Great Society. In the early 1980s, Ronald Reagan successfully converted numerous categorical grants into a series of block grants, slashing funding for several social safety net programs. Block-granting allows conservative opponents of the postwar welfare state to gradually erode funding and grant more authority to state governments, thus using federalism as a more palatable political weapon to reduce social welfare spending than the full dismantlement of social programs. However, despite a flurry of successes in the early 1980s, block-granting has not proven as successful as conservatives might have hoped, and recent efforts to convert programs such as Medicaid and parts of the Affordable Care Act into block grants have failed. The failure of recent failed block grant efforts highlights the resilience of liberal reforms, even in the face of sustained conservative opposition. However, conservatives still draw upon the tool today in their efforts to erode and retrench social welfare programs. Block-granting has thus transformed from a bipartisan tool to improve bureaucratic effectiveness into a perennial weapon in conservatives’ war on the welfare state.