Roman tradition credited King Numa Pompilius, the semi-legendary second king of Rome, with founding the College of Pontiffs as the body responsible for Rome's sacred law, its religious calendar, and the correct performance of state ritual. Unlike the specialized flamines, each tied to a single god's cult, the pontifices held general oversight across the whole of Roman public religion, ruling on questions of sacred versus secular law, burial practice, adoption and inheritance where these touched religious obligation, and the proper form of vows and prayers, functioning in practice as Rome's closest equivalent to a body of religious jurists.
The college was originally small and restricted to patricians, but the Lex Ogulnia of 300 BCE opened it to plebeians and expanded its membership, part of a broader Republican pattern in which formerly closed patrician religious offices gradually admitted plebeian members as the struggle of the orders between Rome's two hereditary classes played out across religious as well as political institutions. By the late Republic the college numbered in the mid teens and its most senior member, the Pontifex Maximus, had become one of the most politically significant religious offices in the Roman state.