The Metacomet Ridge continues west from the isolated Peter's Rock as East Rock, east as Totoket Mountain and southeast as Saltonstall Mountain. Like East Rock, Peter's Rock lies between the main east and west ridges of the Metacomet Ridge. The east side of Peter's Rock drains into the Farm River, thence to the East Haven River and Long Island Sound; the west side into the Quinnipiac River, thence to New Haven Harbor and Long Island Sound.