The Coast Salish homeland encompasses most of the Salish Sea watershed which stretches from the Strait of Georgia north of the Fraser River to the southern end of Puget Sound, and encompasses the modern-day cities of Vancouver and Seattle, among many others. Archeological evidence indicates that the Coast Salish may have inhabited the area as far back as 9000 BC. What is now Seattle, for example, has been inhabited since the end of the last glacial period (8 - 10,000 years ago).

Neighboring groups, whether villages or adjacent tribes, were related by marriage, feasting, ceremonies, and common or shared territory. Ties were especially strong within the same waterway or watershed. Unlike hunter-gatherer societies widespread in North America, but similar to other Pacific Northwest coastal cultures, Coast Salish society was complex, hierarchical and oriented toward property and status. Warfare for the southern Coast Salish was primarily defensive, with occasional raiding into territory where there were no relatives. The Coast Salish held slaves as simple property and not as members of the tribe. The children of slaves themselves became slaves. The real enemies of the Coast Salish for most of the first half of the 19th century were the Kwakwaka'wakw who occupied the territory from Campbell River northward. The Kwakwaka'wakw had earlier access to guns which they acquired by overland trade with Chief Maquinna and his people in Nootka Sound, who were engaged in the fur trade.

The highest-ranking male assumed the role of ceremonial leader but rank could vary and was determined by different standards. Villages were linked to others through intermarriage; the wife usually went to live at the husband's village. Society was divided into upper class, lower class and slaves, all was largely determined by heredity. Nobility was based on genealogy, intertribal kinship, wise use of resources, and possession of knowledge about the workings of spirits and the world.

Belief in guardian spirits and transformation between human and animal was widely shared. The relations of soul or souls, the lands of the living and the dead, were complex and mutable. Vision quest journeys involving other states of consciousness were varied and widely practiced. The Duwamish, for example, had a soul recovery and journey ceremony.

Villages were typically located near navigable water for easy transportation by dugout canoe. Houses that were part of the same village sometimes stretched for several kilometers along a river or watercourse. The villages typically consisted of split cedar-plank longhouses and earthen floors providing habitation for forty or more people, usually a related extended family. Some of these longhouses were extraordinarily large, reaching dimensions of up to 150 x 20 meters. Semi-subterranian houses were also used by many groups. The interior walls of longhouses were typically lined with sleeping platforms. Storage shelves above the platforms held baskets, tools, clothing, and other items. Firewood was stored below the platforms. Mattresses and cushions were constructed of woven reeds and animals skins. Food was hung to dry from the ceiling. The larger houses included partitions to separate families and each family maintained its own interior fire. Roof planks above each fire could spread apart to allow smoke to escape.

Subsistence was based primarily on fishing but also on hunting and gathering. The greatest amount of food was provided by salmon which were available in different regions at different times, depending upon species and proximity to spawning streams. Salmon were take by trolling and jigging, and also by using harpoons, leisters, gaff hooks, dip nets, basket traps, and weirs. They also developed a complex technology called reef netting. This involved anchoring one end of a rectangular net to a reef and the other end between two canoes. The net would rise up to the surface between the canoes in such a way as to resemble a rising reef. As salmon rose to the surface following the artificial reef they could be scooped from the water with dip nets.

Hunting of mammals took place on both water and land. Using harpoons, bows, and nets hunters caught seals, porpoise, and many species of waterfowl including geese, marsh ducks, and grouse. Land mammals hunted included deer, elk, and black bear. From the intertidal zone women gathered sea urchins, barnacles, crabs, butter clams, horse clams, littleneck clams, cockles, and bay mussels. At least 40 different plants were gathered for their edible sprouts and stems, bulbs and roots, berries, fruits, and nuts.