We use a social experiment to estimate the impact of expanding health insurance coverage on the health and mortality of newly entitled SSDI beneficiaries who lacked health insurance. Our intent-to-treat estimates show that expanding health insurance has significant effects on self-reported health at one year following health insurance enrollment, positive effects on mental health and physical health at one year following health insurance enrollment, and no significant effects on mortality within our observation period. About 30% of control group members obtained health insurance coverage within one year following enrollment. We use two-stage least square models to estimate the impact on those who would not have obtained health insurance coverage without the demonstration project and find larger effects on self-reported health and mental health among these SSDI beneficiaries. Finally, we examine distributional impacts to show that mean impacts miss meaningful effects.