Bristol Bay (Iilgayaq in Central Yup'ik) is the eastern-most arm of the Bering Sea, at 57° to 59° North 157° to 162° West in Southwest Alaska. Bristol Bay is 400 km (250 mi) long and 290 km, (180 mi) wide at its mouth. A number of rivers flow into the bay, including the Cinder, Egegik, Igushik, Kvichak, Meshik, Nushagak, Naknek, Togiak, and Ugashik.
Upper reaches of Bristol Bay experience some of the highest tides in the world. One such reach, the Nushagak Bay near Dillingham and another near Naknek in Kvichak Bay have tidal extremes in excess of 10 m (30 ft), ranking them — and the area — as eighth highest in the world. This, coupled with the extreme number of shoals, sandbars and shallows, makes navigation troublesome, especially during the area's frequently strong winds. As the shallowest part of the Bering Sea, Bristol Bay is one of the most dangerous areas for large vessels.
In ancient times, much of Bristol Bay was dry and arable, along with much of the Bering Sea Land Bridge. More recently, its proximity to mineral, animal and seafood riches provided incentive for human habitation along its shoreline. Early Russian and English exploration provided most of the non-native influences of the area. During his voyage through the area in 1778, the famed British navigator and explorer, Captain James Cook named the area "in honor of the Admiral Earl of Bristol" in England.
After establishing some temporary settlements in the late 1790s, The Russian American Company sent exploratory parties to document the coast and nearby inland areas of Bristol Bay. One of these charted the area between the Kuskokwim and Nushagak Rivers. Later, in 1819, an Aleut by the name of Andrei Ustiugov drew the first intensive charts of Bristol Bay. Additionally, ships of the Russian Navy conducted extensive surveys of the Bering Sea coastline into the mid-19th century, naming many of the geographical features commonly used today: Capes Constantine, Chichagof, Menshikof and Greig, Mounts Veniaminof and Pavlof, Becharof Lake, etc.