The Geisel School of Medicine is the medical school of Dartmouth College, an Ivy League research university located in Hanover, New Hampshire, United States. The fourth-oldest medical school in the United States, it was founded in 1797 by New England physician Nathan Smith and grew steadily over the course of the 19th century. Several milestones in medical care and research have taken place at Dartmouth, including the first clinical X-ray (1896), the first intensive care unit in the United States (1955), and the Brattleboro rat (1961).