The Curtis Institute of Music is a conservatory in Philadelphia, Pennsylvania, that offers courses of study leading to a performance Diploma, Bachelor of Music, Master of Music in Opera, and Professional Studies Certificate in Opera. According to statistics compiled by U.S. News & World Report, it has the lowest acceptance rate of any college or university, making it the most selective institution of higher education in the United States. It was established in 1924 by Mary Louise Curtis Bok, and was named in honor of her father, Cyrus Curtis. After consulting with musician friends including Josef Hofmann and Leopold Stokowski on how best to help musically gifted young people, Bok purchased three mansions on Philadelphia's Rittenhouse Square and had them joined and renovated. She established a faculty of prominent performing artists and eventually left the institute with an endowment of US$12 million.