Puget Sound is an arm of the Pacific Ocean, connected to the rest of the Pacific by the Strait of Juan de Fuca, in the Pacific Northwest of the United States. It branches out from Admiralty Inlet and Deception Pass in the north to Olympia, Washington in the south. The surrounding land partially overlaps the Seattle metropolitan area, home to about 4 million people.
In 1792 George Vancouver gave the name "Puget's Sound" to the waters south of the Tacoma Narrows, in honor of Peter Puget, then a lieutenant accompanying him on the Vancouver Expedition. The name later came to be used for the waters north of Tacoma Narrows as well.
The USGS defines Puget Sound as all the waters south of three entrances — the main entrance at Admiralty Inlet being a line between Point Wilson, on the Olympic Peninsula, and Point Partridge, on Whidbey Island; a second entrance at Deception Pass being a line from West Point, on Whidbey Island, to Deception Island and Rosario Head, on Fidalgo Island; and a third entrance at the south end of the Swinomish Channel, which connects Skagit Bay and Padilla Bay. Under this definition, Puget Sound includes the waters of Hood Canal, Admiralty Inlet, Possession Sound, Saratoga Passage, and others. It does not include Bellingham Bay, Padilla Bay, the waters of the San Juan Islands or anything farther north.
Another definition, given by NOAA, subdivides Puget Sound into five basins or regions. Four of these correspond to areas within the USGS definition, but the fifth one, called "Northern Puget Sound" includes a large additional region. It is defined as bounded to the north by the international boundary with Canada, and to the west by a line running north from the mouth of the Sekiu River on the Olympic Peninsula. Under this definition significant parts of the Strait of Juan de Fuca and the Strait of Georgia are included in Puget Sound, with the international boundary marking an abrupt and hydrologically arbitrary limit.
According to Arthur Kruckeberg, the term "Puget Sound" is sometimes used for waters north of Admiralty Inlet and Deception Pass, especially for areas along the north coast of Washington and the San Juan Islands, essentially equivalent to NOAA's "Northern Puget Sound" subdivision described above. Kruckeberg uses the term "Puget Sound and adjacent waters".
An alternative term for Puget Sound, still used by only some Native Americans and environmental groups, is Whulge (or Whulj), an Anglicization of the Lushootseed name 'WulcH, which means "Salt Water".. Another neologism also popularized by environmental and aboriginal groups is Salish Sea, but this does not have wide acceptance nor a single standard meaning from one group to the next. Sometimes the terms "Puget Sound" and "Puget Sound and adjacent waters" are used for not only Puget Sound proper but also for waters to the north, such as Bellingham Bay and the San Juan Islands region.
George Vancouver explored Puget Sound in 1792. Vancouver claimed it for Great Britain on 4 June 1792, naming it for one of his officers, Lieutenant Peter Puget. It became part of the Oregon Country, and became U.S. territory when the 1846 Oregon Treaty was signed.
After arriving along the Oregon Trail, many settlers wandered north to what is now Washington State and settled the Puget Sound area. The first non-Aboriginal settlement was New Market (now known as Tumwater) in 1846. In 1853 Washington Territory was formed from part of Oregon Territory. In 1888 the Northern Pacific railroad line reached Puget Sound, linking the region to eastern states.
For a long period Tacoma was noted for its large smelters where gold, silver, copper and lead ores were treated. Seattle was the primary port for trade with Alaska and the rest of the country and for a time possessed a large shipbuilding industry. The region around eastern Puget Sound developed heavy industry during the period including World War I and World War II, and the Boeing Company became an established icon in the area.
During World War II the Puget Sound area became a focus for the war industry, with Boeing producing many of the nation's heavy bombers and the ports of Seattle, Bremerton and Tacoma available for shipbuilding.
The United States Geological Survey (USGS) defines Puget Sound as a bay with numerous channels and branches; more specifically, it is a fjord system of flooded glacial valleys. Puget Sound is part of a larger physiographical structure termed the Puget Trough, which is a physiographic section of the larger Pacific Border province, which in turn is part of the larger Pacific Mountain System.
Puget Sound is a very large salt water estuary, or system of many estuaries, fed by highly seasonal freshwater from the Olympic and Cascade Mountain watersheds. The northern boundary is Admiralty Inlet, between Point Partridge on Whidbey Island and Point Wilson on the Olympic Peninsula. A second entrance is Deception Pass, between West Point on Whidbey Island and Rosario Head on Fidalgo Island.
The Sound has been reshaped by the scouring action and till deposition of the Wisconsin Glaciation, which extended in this region as far south as Olympia; the soils of the region, less than ten thousand years old, are still characterized as immature. During glacial maximum a large meltwater lake formed at the icewall's forefront, drained by the Chehalis River; its sediments form the blue-gray clay identified as the Lawton Clay. As icebergs calved off the toe of the glacier, their embedded gravels and boulders were deposited in the chaotic mix of unsorted till geologists call glaciomarine drift. Many beaches about the Sound display glacial erratics, rendered more prominent than those in coastal woodland solely by their exposed position; submerged glacial erratics sometimes provide hazards to navigation. The sheer weight of glacial-age ice depressed the landforms, which experienced isostatic rebound after the ice sheets had retreated; because the rate of rebound was not synchronous with the post-ice age rise in sea levels, the bed of what is Puget Sound, filled alternately with fresh and with sea water. The upper level of the lake-sediment Lawton Clay now lies about 120 feet (37 m) above sea level.
The Puget Sound system consists of four deep basins connected by shallower sills. The four basins are Hood Canal, west of the Kitsap Peninsula, Whidbey Basin, east of Whidbey Island, South Sound, south of the Tacoma Narrows, and the Main Basin, which is further subdivided into Admiralty Inlet and the Central Basin. Puget Sound's sills, a kind of submarine terminal moraine, separate the basins from one another, and Puget Sound from the Strait of Juan de Fuca. Three sills are paricularly significant — the one at Admiralty Inlet which checks the flow of water between the Strait of Juan de Fuca and Puget sound, the one at the entrance to Hood Canal (about below the surface), and the one at the Tacoma Narrows (about ). Other sills that present less of a barrier include the ones at Blake Island, Agate Pass, Rich Passage, and Hammersley Inlet.
The depth of the basins is a result of the Sound being part of the Cascadia subduction zone, where the terranes accreted at the edge of the Juan de Fuca Plate are being subducted under the North American Plate: there has not been a major subduction zone earthquake here since the magnitude nine Cascadia Earthquake; according to Japanese records, it occurred 26 January 1700. Lesser Puget Sound earthquakes with shallow epicenters, caused by the fracturing of stressed oceanic rocks as they are subducted still cause great damage. The Seattle Fault cuts across Puget Sound, crossing just north of Vashon Island and dipping under the city of Seattle . To the south, the existence of a second fault, the Tacoma Fault has buckled the intervening strata in the Seattle Uplift.
Typical Puget Sound profiles of dense glacial till overlying permeable glacial outwash of gravels above an impermeable bed of silty clay may become unstable after periods of unusually wet weather and slump in landslides.
The urban region designated the Puget Sound Region is centered on Seattle, Washington, and consists of nine counties, two urban center cities and four satellite cities making up what has been dubbed "Pugetopolis". Both urban core cities have large industrial areas and seaports plus a high-rise central business district. The satellite cities are primarily suburban, featuring a small downtown core and a small industrial area or port. The suburbs consist mostly of residences, strip malls, and shopping centers. The region is also home to numerous ports. The two largest and busiest are the Port of Seattle and Port of Tacoma, which, if combined, comprise the second largest container port in North America after Los Angeles/Long Beach.
A unique state-run ferry system, the Washington State Ferries, connects the larger islands to the Washington mainland, as well as both sides of the sound, allowing cars and people to move about the greater Puget Sound region.