Sisters Rocks, also known historically as Three Sisters Rocks, is a minor headland between Mussel Creek to the north and Eucher Creek to the south, at the site of the historical town of Frankport, about 13 miles (21 km) north of Gold Beach and 11 miles (18 km) south-southeast of Port Orford, Oregon. Sisters Rocks consists of three isolated peaks, two are attached to the mainland, and the third is offshore about 700 feet (210 m) to the southwest. Sisters Rocks and much of the southern Oregon coast is part of the Otter Point Formation, a complex assemblage of Late Jurassic or Early Cretaceous bounded almost everywhere by faults. The formation is named after a headland about 3 miles (5 km) north of the Rogue River and consists of mudstone, argillite, and clay and contains scattered highly sheared blocks of exotic sandstone, metavolcanic greenstone, radiolarian chert, and schist. Although its original thickness is unknown, it is assumed to have been thousands of feet. Because of the pervasive fault shearing, lack of preserved stratigraphic order, and the presence of exotic rock masses, the Otter Point Formation is considered to be a tectonostratigraphic complex or mélange. Otter Point Formation is regarded as a subduction complex where sediments called turbidites were deposited on the slope of a Late Mesozoic arc trench along the western margin of North America. These turbidites include not only trench fill sediments, but also abyssal plain sediments deposited on the sea floor beyond the trench, indicated by the presence of radiolarian chert, and slope-basin deposits perched on the accretionary trench slope. The present-day Sisters Rocks were formed when part of an ancient headland was eroded by the hydraulic action of waves which forced seawater into rock fractures, eventually creating sea caves and arches that collapse to form free-standing stacks or small islands. Eventually, wave erosion will continue breaking down the stack until only a reef or wave-cut platform remains.

The Tututni people are a historical Lower Rogue River Athabascan tribe who traditionally inhabited the Pacific Coast between the Coquille River in the north and the Chetco River in the south. Cosutt-Hentens was a Tututni band that lived between Humbug Mountain in the north to Sister Rocks in the south and had one village at Mussel Creek. The Eu-qua-chees band lived from Sister Rocks south to Nesika Beach and had one village at Euchre Creek. The meaning of the name is no longer known. In the late 1700s, British, Spanish, and American ships explored the coast of Oregon, and in 1792, Captain George Vancouver made contact and traded with some Tututni. Merchants engaged in the maritime fur trade followed and traded with the Tututni for sea otter pelts. Infectious diseases resulted in the deaths of 75 to 90 percent of the Oregon native peoples since they had no immunity to smallpox, measles, influenza, and many other diseases that were common among Europeans and Americans. In the 1840s, the first wagon trains carrying immigrants started arriving overland in Oregon, but the region remained peaceful until the 1850s when Tututni game trails and hunting grounds were destroyed by whites clearing lands for farms. The Tututni women were corrupted by trappers and miners, and white ferrymen pre-empted the exclusive Tututni river-crossing businesses. In 1855, a treaty between Oregon Superintendent of Indian Affairs Joel Palmer and the Tututnis required them to surrender 2.5 million acres (1 million ha) but it was not ratified by Congress resulting in the Rogue Wars. White settlers at Port Orford were attacked by the Tututni, while other tribes up the Rogue River were urged to join in the war against the settlers. In 1856, the Tututnis reportedly killed 26 people including an Indian agent and the conflict continued as they burned most of the settlers’ homes between Port Orford and Smith River. In 1857, about 600 Tututni, Chetco, Coquille, Chastacosta, Takelma, and Latgawa tribesmen and a few Shastas were herded aboard a steamer and shipped up the coast, and then marched over the Coast Range to an alien home on the Grand Ronde Reservation. They remained there for a year and then moved to the Siletz Reservation, also called the Coast Reservation, but by this time their population had dwindled to only a few hundred. By 1964, only 6 people remained who spoke the native language.

Early ranches in the area of Sisters Rocks included John O’Brien’s Three Sisters Ranch and Herman Francis Reinhart’s Pacific Ranch. As early as the 1850s, the small cove formed by Sisters Rocks served as one of the few safe harbors for boats caught by high northwesterly winds and seas between Gold Beach and Port Orford. The small harbor was the site of land speculation and business ventures among early settlers who needed sheltered beach landings. The S.H. Frank Company developed the site in 1893 into a local shipping point for a large tannery in Redwood City, California. During the 19th century, tanoak was cut commercially and the logs were stripped of bark for the extraction of tannin which was necessary for curing hides to make leather. The company bought large tracts of local tanoak forest in the 1860s, as well as the oceanfront property at Sisters Rocks, and used steam and sail schooners to transport tanoak bark to Redwood City. The bark was harvested during a summer window of about six weeks when peeling bark from freshly cut trees was feasible. The dock workers, often local residents, labored as wood crews, teamsters, and longshoremen. Frankport consisted of a barn, a bunkhouse, and storage buildings. The tanoak business collapsed by the end of the 19th century due to overcutting that left few trees large enough for tannin production. The Frank Company stopped using the port in about 1901. Clayton Mark of Chicago purchased both the forestland and the Frank property at Sisters Rocks in the 1920s, with an eye toward logging his 30,000-acre holdings and shipping the logs from Frankport, but the project never got started and Frankport remained abandoned. Sause Brothers Ocean Towing Company of Coos Bay bought the Frankport land in 1955. The dock was rebuilt in 1958 to handle loading equipment and log trucks to ship whole old-growth logs. The company also shipped quarry rock and aggregate from 1956 to 1969. The rock was used to repair the south jetty on the Rogue River, as well as for riprap and road projects. In 2003, the 76 acres (31 ha) of property were purchased by Oregon State Parks and is now named the Sisters Rocks State Park. Read more here and here. Explore more of Sisters Rocks  and Frankport here: