As a result of the 1944 PHS Act’s authorization to conduct clinical research, NIH obtained funding after the war to build a research hospital on its Bethesda campus. President Harry Truman laid the cornerstone in 1951. Opened in 1953, the facility was called the "NIH Clinical Center." Patients could come only by referral from a physician to participate in a research study. The Clinical Center’s 540 beds made it the largest research hospital in the world.