You searched for: Institution University of Michigan. Libraries Remove constraint Institution: University of Michigan. Libraries Place Sister Rocks 7.5' quad. North Coast. Marsh on north side of Hwy 101, 1.0 km northwest of Humboldt Road, about 2.1 km southeast of Crescent City, north-northeast side of the marsh. Remove constraint Place: Sister Rocks 7.5' quad. North Coast. Marsh on north side of Hwy 101, 1.0 km northwest of Humboldt Road, about 2.1 km southeast of Crescent City, north-northeast side of the marsh.