The Flat Islands are situated about 0.8 miles (1.3 km) offshore and 1 mile (1.6 km) north of Point Bede on the Kenai Peninsula along the southern shore of Kachemak Bay in southern Cook Inlet, about 31 miles (50 km) south of Anchor Point and 3 miles (5 km) southwest of Nanwalek, Alaska. William H. Dall gave them their descriptive name in 1880, which the US Coast and Geodetic Survey published on charts. The islands are treeless and grass-covered, consisting of two islands connected by a reef that is exposed at low tide and surrounded by a bull kelp forest. Point Adam lies about 5 miles (8 km) to the south; Captain James Cook originally named that headland Cape Bede in 1778 after Saint Bede, but the Coast and Geodetic Survey renamed it in 1908. The southwestern end of the Kenai Mountains represents the Peninsular terrane, which developed as an island arc during the Triassic and Jurassic periods, about 200 million years ago. A quartz diorite pluton intruded the terrane during the Jurassic (200 million to 145 million years ago) and accreted to North America by the Early Cretaceous, about 140 million years ago. This pluton, exposed at Point Bede and the Flat Islands, consists of plagioclase, quartz, biotite, and hornblende, which resist erosion.

The Chugach Sugpiaq people inhabited the outer coast of the Kenai Peninsula between Prince William Sound and Port Graham, living in semi-permanent settlements. In the mid-1780s the Russian fur trade exploited sea otters along the outer Kenai Peninsula, establishing trading posts at Cape Douglas, Nuchek and at Alexandrovsk (present-day Nanwalek). The Chugach Sugpiaq left their traditional settlements in the 1880s and moved to these trading centers for jobs, schools and Russian Orthodox churches, but continued using their traditional sites for seasonal hunting, trapping and fishing. Salteries and canneries were established in the late 1800s and early 1900s by some of the same companies that had operated fur-trading posts. The first salmon trap was built in Cook Inlet around 1885, patterned after the pound nets used in the Great Lakes fisheries. This type became known as a pile trap because whole-log piles were driven into sandy bottoms to support the trap, and webbing and wire netting were fastened to vertical piles to form walls. By the 1930s Fidalgo Island Packing Company operated a cannery at Port Graham and 4 fish traps in Kachemak Bay: one on the north shore between Travers Creek and Diamond Creek, and three on the south shore at MacDonald Spit, Point Naskowhak and in the channel between Flat Island and the Kenai Peninsula.

The Flat Islands form a good radar target, providing an important navigational aid for large vessels bound for Kachemak Bay or upper Cook Inlet. The Flat Island Light sits on a skeleton tower 70 feet (21 m) above the water, with a red-and-white diamond-shaped daymark on the northwest point of the northernmost island. In 2002 the Kachemak Bay Research Reserve partnered with the National Data Buoy Center of the National Weather Service, part of the National Oceanic and Atmospheric Administration, to establish a weather station on Flat Island. The Coastal-Marine Automated Network (C-MAN) weather station is part of a meteorological observation network along America’s coast. The network consists of about 60 stations on lighthouses, at capes and beaches, on nearshore islands and on offshore platforms. The stations record atmospheric pressure, wind direction, speed and gust, and air temperature. Some also measure sea-surface temperature, water level, waves, relative humidity, precipitation and visibility. Data from the C-MAN station at Flat Island are telemetered and ingested into numerical weather-prediction computer models. Read more here and here. Explore more of the Flat Islands and Kachemak Bay here: