This article analyzes social change in the emerging colonial world of the lower Columbia River from 1805 to 1838, particularly regarding gender and sexuality. It teases out distinctions among formal marriages, informal “custom of the country” arrangements, the exercise of sexual “liberties” by young Chinookan women, and prostitution, revealing much of the complex sexual interactions between natives and newcomers. Such a focus illuminates critical, interpersonal aspects of fur trade society in this region as it developed into a complex colonial milieu, reflecting both indigenous and Western interests. Lower Chinookans adapted slavery and trade practices to accommodate the demands of their own social stratification and the challenges brought by newcomers. Colonial accommodations were first limited by Western racial and economic ideologies, and subsequently by the gross power inequity caused by the collapse of the native population in the early 1830s from malaria and other introduced diseases.