John I. Hart was born in 1786 Portsmouth, England, where his father, Judah, worked as a silversmith. He married Maria Levy—aunt of Arthur Lumley Levy—with whom he had seven children. The family came to the United States around 1818.
In 1825 Hart was one of a committee to request and receive aid from Shearith Israel for the founding of B’nai Jeshurun, New York’s second synagogue and the first to practice an Ashkenazi rite. He also worked with the Mutual Benefit and Burial Society. In 1822, Hart and Joseph Davies took up a collection for the medical care of a Jewish Revolutionary War veteran who, with neither money nor family, had fallen sick while visiting New York. The veteran died before the money could be put to use, so with the collected $300, the Hebrew Benevolent Society of New York was founded.
In 1852, joined by Henry Hendricks among others, Hart became one of the founders of Mount Sinai Hospital, known at the time as the Jews Hospital. He served as well as the first vice president of the hospital, originally located on a West 28th lot donated by Sampson Simson, with a bequest of 20,000 dollars to the board of trustees from Judah Touro.
