To the first question: the PNW was the most densely populated region in North America at the time of contact. The richness of the seas and the temperate rainforests supported enormous populations impossible elsewhere on the continent. To the second: extensively. The Haida were the traders par excellence of the region; their trade canoes wandered the coast from California (source of much-coveted abalone) to Washington (source of slaves from the Nuu-chah-nulth, Salish, and other "Flathead" Indians) to British Columbia (source of fine Chilkat blankets and transformation masks from the Tsimshian and Kwakwaka'wakw) to Alaska (source of sea otter pelts, bear pelts, and drift iron tools from the Tlingit, as well as goods from Aleuts to the north and Athabaskan tribes from the Interior). While not firmly demonstrated, some scholars believe Haida Gwaii may have also had intermittent contact with Kamchatka in Siberia based on certain shared folktales and customs.