Why did Northwest Coast Indian populations decline so sharply between 1780 and 1900?

Between 1780 and 1900, the indigenous population of the Northwest Coast experienced a severe decline of as much as 80 percent, primarily driven by the introduction of contagious diseases to which the native peoples had no prior exposure.1

The most disruptive events during this period were epidemics of illnesses such as smallpox, measles, and venereal infections. These outbreaks had a profound impact on native society, resulting in extremely high mortality rates. The loss of life was so significant that it caused a collapse of social systems, as the deaths of elders and knowledge-holders led to the loss of vital ritual and practical information. Furthermore, the resulting depopulation forced societies to adopt unusual social structures, such as the allocation of multiple titles to single individuals, to maintain continuity.1

While these epidemics were the primary cause of the sharp population drop, the broader context of colonialism also contributed to the suffering of indigenous peoples through displacement, battles, and the secondary effects of famine and starvation.21