Castle Cape extends about 10 miles (16 km) northeast from the Alaska Peninsula and forms the southern entrance to Chignik Bay, separating Castle Bay to the northwest from the Pacific Ocean to the southeast, about 45 miles (72 km) northeast of Perryville and 9.5 miles (15 km) southeast of Chignik, Alaska. The point at the end of the cape is officially named Tuliumnit Point but is locally known as Castle Cape, according to the US Geological Survey in 1911. The cape was first described in 1898 by Lieutenant Commander Jefferson F. Moser of the US Navy, aboard the US Bureau of Fisheries steamer Albatross. Rising over 1,200 feet (366 m), Castle Cape is distinguished by a turreted summit and sharply stratified rock, displaying alternating dark and light layers. This striking formation serves as a prominent navigational landmark for passing ships. The deep embayments extending southwest from the cape, known as the Castle Cape Fjords, are flanked by extremely rugged mountains carved by the sea. These rocks belong to the Peninsular terrane, a structural geological unit underlying much of the Alaska Peninsula. The Peninsular terrane is a Triassic to Jurassic island-arc complex that was accreted to the North American plate by the Early Cretaceous. The terrane includes the Iliamna and Chignik formations. The Late Cretaceous Chignik formation is exposed along the south side of Chignik Bay, between Chignik Lagoon and Castle Cape. It comprises a cyclic sequence of sedimentary rocks: shallow to nearshore marine deposits in the lower section and primarily continental deposits in the upper section. The formation consists of sandstones, shales, conglomerates, and occasional thin coal beds, reaching a thickness of at least 1,968 feet (600 m) in the Chignik Bay region. Fossilized plants and shells confirm its Late Cretaceous age. Notably, sandstone from the formation north of Castle Cape has also yielded hadrosaur tracks.

Archaeological sites about 100 miles (161 km) northeast of Chignik indicate human presence on the northeast Alaska Peninsula for at least 9,000 years. Additional sites 50 miles (80 km) northeast show occupation from 2,000 to 300 years ago, while those 60 to 200 miles (97–322 km) southwest indicate continuous use over the past 5,000 to 6,000 years. Most settlements in the Chignik region, both historical and prehistoric, are near productive salmon streams. Stone tools, including notched net sinkers, suggest a longstanding reliance on fishing—likely for salmon. The first recorded Western expedition to the Pacific coast of the Alaska Peninsula came in 1741, when Vitus Bering sought land and resources for Russia. A second expedition in the 1760s brought fur traders who soon dominated Indigenous populations. These Russians encountered Aleut Unangan speakers from the west and southwest and Yup’ik-speaking ancestors of the Alutiiq Sugpiat from the central and eastern peninsula. Scholars believe the cultural boundary between these groups lay near Chignik. The Alutiiq were maritime hunters whose homeland included the southern Alaska Peninsula, Kodiak Island, lower Cook Inlet, and Prince William Sound. They relied on marine and tundra resources for food, fuel, and raw materials and were adept at using seal-skin kayaks (bidarkas) and open boats. Their hunting skills made them targets for Russian exploitation; many Alutiiq men were forced into labor. Russians introduced Christianity, trade goods, and diseases to which Alaska Natives had no immunity. The Alutiiq population suffered devastating losses in the 18th and 19th centuries. Russian exploitation persisted until the Alaska Purchase in 1867, after which American interests focused on whaling, fur, and commercial fishing. Chignik’s first salmon cannery opened in 1888. By 1890, salmon fishing had become the region’s dominant industry. All five species of Pacific salmon are harvested in the commercial fishery, with sockeye being the most important species in this region. Between 2000 and 2018, declines in salmon abundance prompted closures of the Chignik area salmon fisheries resulting in regional population declines of at least 31 percent.

Castle Cape has long served as a distinctive landmark for mariners navigating Alaska’s treacherous coastline. It is so well known that the US National Weather Service uses it as a reference point to divide marine forecast zones: Area 150 spans from Sitkinak Island to Castle Cape, and Area 155 from Castle Cape to Cape Sarichef. The National Weather Service Marine Program provides forecasts and warnings for US coastal and offshore waters. Its origins date to 1870, when a congressional resolution directed the Secretary of War to collect meteorological observations and provide storm warnings. A formal marine weather program began on January 23, 1873, under the US Army Signal Corps, which transcribed meteorological data from ships arriving in port. In 1890, the US Weather Bureau became a civilian agency under the Department of Agriculture. The US Navy began issuing North Atlantic marine forecasts in 1901, and this responsibility was transferred to the Weather Bureau in 1904. In the early 20th century, the Norwegian cyclone model helped meteorologists understand mid-latitude atmospheric structure. Combined with an increase in shipboard observations, it enabled the first crude atmospheric maps. During World War II, the US Navy established a marine weather center, and the US Coast Guard created manned ocean weather stations. In 1957, the Weather Bureau began publishing the Mariners Weather Log, which continues today. The Weather Bureau became the National Weather Service in 1970. Today, individual forecast offices—including three in Alaska—issue marine forecasts and warnings for nearshore coastal waters. Read more here and here. Explore more of Castle Cape and Chignik Bay here: