By 1850, the Native American population had been greatly reduced by disease and forced removal, and the first major wave of EuroAmerican settlement was underway. These early settlers were powerfully drawn to floodplains for fertile agricultural soils and to rivers for energy and transportation. The resulting location of early cities has left a legacy that persists today. The highest population densities occur along the Willamette River and particularly at the confluences of the major rivers: in Eugene (Coast Fork Willamette, Middle Fork Willamette, and McKenzie Rivers), Corvallis/Albany (Marys, Calapooia, and Willamette Rivers), Salem (Willamette River), and Portland (Willamette, Clackamas, and Columbia Rivers). These areas of population growth coincide with some of the most productive agricultural land in the basin.

The total population has increased each decade from 1850 to the present-day, although the rate of growth has fluctuated with changing economic and social conditions. The spatial distribution of the population has likewise shifted. As the economy has gradually changed from a resource-based economy, mainly forestry and farming, to a high-tech manufacturing and information-based economy, population growth has been increasingly concentrated in urban areas, where most jobs are located, and nearby residential areas. The U.S. Bureau of the Census defines an urbanized area as composed of one or more places with a minimum of 50,000 people and a density of at least 1,000 people per square mile. By 1990, over 80% of the basin's population lived in areas with 1,000 or more people per square mile. Areas within city limits occupied 4% of the total area in the Willamette Basin.

Excerpted with permission from Branscomb, A., Richmond, M., Dearborn, H and J. Guicochea Duclos. Human Population. (2002) In D. Hulse, S. Gregory, and J. Baker (Eds.). Willamette River Basin planning atlas, 2nd. Edition, (p.51). Corvallis: Oregon State University Press, 2002