We assess the causal effect of the National Kidney Registry (NKR), the largest national kidney-exchange network in the U.S., on kidney-exchange outcomes. Analyzing a unique database hosted by the Scientific Registry of Transplant Recipients (SRTR) that contains information on all kidney donors, wait-listed candidates, and transplant recipients in the U.S., we find that patients in an NKR hospital are 2.5 to 3 times more likely than their counterparts in a non-NKR hospital to receive a transplant from a living donor, conditional on wait-time. At the same time, NKR participation does not have a significant effect on the desirability of donors and the health status of recipients. We employ various approaches to ensure our finding is robust in addressing the non-random sorting of patients and donors. As far as the outcomes we study, the expansion of the NKR brings about an overall positive impact on the kidney exchange market.