Steep Hill Brook is a short tributary of Six Mile Run in Franklin Park, Somerset County, New Jersey. Rising in a pond near Amwell Road and Van Cleef Road at Scott Farm, it flows south through the preserved Six Mile Run Reservoir Site, passes under Blackwells Mills Road, and joins Six Mile Run. Its channel is marked by fine reddish gravel, frequent gravel bars, and some shale cliffs along the banks. The brook is generally shallow and medium-fast, creating oxygen-rich water for fish, while frogs favor slower sections. Within preserved land near roads and farmland, it retains a quiet, semi-natural character.