We quantify the cost savings from the Acid Rain Program (ARP) by comparing compliance costs for 761 coal-fired generating units under the ARP with compliance costs under a counterfactual uniform performance standard (UPS) that would have achieved the same aggregate emissions in 2002. In 2002, we find compliance costs to be $200 million (1995$) lower and health damages to be $170 million (1995$) lower under the ARP. We also compare health damages associated with observed SO₂ emissions from all ARP units in 2002 with damages from a no-trade counterfactual. Damages under the ARP are $2.1 billion (1995$) higher than under the no-trade scenario, reflecting allowance transfers from units in the western US to units in the eastern US with larger exposed populations.