Sisters Rocks, historically known as Three Sisters Rocks, is a minor headland located between Mussel Creek to the north and Eucher Creek to the south, about 13 miles (21 km) north of Gold Beach and 11 miles (18 km) south-southeast of Port Orford, Oregon. The formation is also the site of the historical town of Frankport. It 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 are part of the Otter Point Formation, a complex assemblage of Late Jurassic or Early Cretaceous rocks bounded almost everywhere by faults. Named after a headland about 3 miles (5 km) north of the Rogue River, the formation consists of mudstone, argillite, and clay, containing 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. Due to pervasive fault shearing, lack of preserved stratigraphic order, and the presence of exotic rock masses, the Otter Point Formation is considered a tectonostratigraphic complex or mélange. The Otter Point Formation is a subduction complex where sediments known as turbidites were deposited on the slope of a Late Mesozoic arc trench along North America’s western margin. These turbidites include not only trench-fill sediments but also abyssal plain sediments, as indicated by the presence of radiolarian chert. Additionally, slope-basin deposits were perched on the accretionary trench slope. The present-day Sisters Rocks were formed when an ancient headland was eroded by waves. The hydraulic action of the waves forced seawater into rock fractures, creating sea caves and arches. Over time, these structures collapsed, forming free-standing stacks or small islands. Continued wave erosion will eventually break down the stacks until only a reef or wave-cut platform remains. This process exemplifies the dynamic interactions between geological formations and erosional forces, illustrating the ever-changing coastal landscape.

The Tututni people were 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. The Cosutt-Hentens, a Tututni band, lived between Humbug Mountain in the north and Sister Rocks in the south, with a village at Mussel Creek. The Eu-qua-chees band resided from Sister Rocks south to Nesika Beach and had a village at Euchre Creek. The meaning of the name is unknown. In the late 1700s, British, Spanish, and American ships explored the Oregon coast. In 1792, Captain George Vancouver made contact with some Tututni, trading with them. Maritime fur traders followed, exchanging goods for sea otter pelts. Infectious diseases brought by Europeans and Americans, such as smallpox, measles, and influenza, resulted in the deaths of 75% to 90% of the native population, who had no immunity. In the 1840s, the first wagon trains carrying immigrants arrived overland in Oregon. The region remained peaceful until the 1850s, when settlers destroyed Tututni game trails and hunting grounds to clear land for farms. In 1855, a treaty between Oregon Superintendent of Indian Affairs Joel Palmer and the Tututni tribe required the Tututni to surrender 2.5 million acres (1 million ha). However, Congress did not ratify the treaty, leading to the Rogue Wars. White settlers at Port Orford were attacked by the Tututni, and other tribes along the Rogue River were urged to join the conflict. In 1856, the Tututni reportedly killed 26 people, including an Indian agent, and burned most settlers’ homes between Port Orford and the Smith River. In 1857, about 600 individuals from the Tututni, Chetco, Coquille, Chastacosta, Takelma, and Latgawa tribes, along with a few Shastas, were forcibly relocated. They were shipped up the coast on a steamer and then marched over the Coast Range to the Grand Ronde Reservation. After a year, they moved to the Siletz Reservation, also known as the Coast Reservation. By this time, their population had dwindled to a few hundred. By 1964, only six people remained who spoke the native language.

In the area around Sisters Rocks, early ranches included John O’Brien’s Three Sisters Ranch and Herman Francis Reinhart’s Pacific Ranch. By 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. This small harbor became a site for land speculation and business ventures among settlers who needed sheltered beach landings. In 1893, the S.H. Frank Company developed the site into a local shipping point for a tannery in Redwood City, California. During the 19th century, tanoak was commercially cut, and the logs were stripped of bark to extract tannin, necessary for curing hides to make leather. The company acquired large tracts of local tanoak forest in the 1860s, as well as oceanfront property at Sisters Rocks, using steam and sail schooners to transport tanoak bark to Redwood City. The bark was harvested during a six-week summer window 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. By the end of the 19th century, the tanoak business collapsed due to overcutting, which left few trees large enough for tannin production. The Frank Company ceased using the port around 1901. In the 1920s, Clayton Mark of Chicago purchased both the forestland and the Frank property at Sisters Rocks, intending to log his 30,000-acre (12,140-ha) holdings and ship the logs from Frankport. However, the project never commenced, and Frankport remained abandoned. Sause Brothers Ocean Towing Company of Coos Bay acquired the Frankport land in 1955. The dock was rebuilt in 1958 to handle loading equipment and log trucks for shipping whole old-growth logs. The company also shipped quarry rock and aggregate from 1956 to 1969, which were 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 named Sisters Rocks State Park. Read more here and here. Explore more of Sisters Rocks and Frankport here: