It was compiled by Castle Connolly Medical Ltd., a health care research and information company founded in 1992 by a former medical college board chairman and president to help guide consumers to America’s top doctors and hospitals.

Castle Connolly’s rigorous selection process, under the direction of an MD, involves surveying hundreds of thousands of physicians, as well as academic medical centers, specialty hospitals, and regional and community hospitals across the nation. Online nominating (at castleconnolly.com/nominations) is open to all licensed physicians in America. They are able to nominate physicians in any specialty and in any part of the country, as well as indicate whether those physicians are among the best in their region or the nation in their specialty. The nominated doctors’ educational and professional experience is carefully screened before final selection is made among those physicians most highly regarded by their peers.

After identifying the top doctors in America, Castle Connolly provides consumers with detailed information about their education, training, and expertise in its paperback guides and online directories and in national and regional magazine “Top Doctors” features. Doctors do not and cannot pay to be selected.

Castle Connolly was acquired by digital health care company Everyday Health Group in 2018. EHG, a division of J2 Global Inc., combines social listening data and analytics expertise to deliver personalized health care content and patient-engagement solutions. Its websites have an audience of more than 53 million consumers and more than 780,000 practicing U.S. physicians. Its flagship brands include Everyday Health, What to Expect, MedPage Today, Health eCareers, and PRIME Education, and it has an exclusive partnership with MayoClinic.org and the Mayo Clinic Diet.