Abstract: This dissertation investigates household and community organization at Sx&barbelow;wóx&barbelow;wiymelh, an early Northwest Coast pithouse village in Upper Stó:lō (Coast Salish) territory, located within the Upper Fraser Valley of southern British Columbia. In this work, I address the socioeconomic constitution of the Sx&barbelow;wóx&barbelow;wiymelh community and its households, provide an explanation for population coalescence at this location, and explore the broader processes of socioeconomic and sociopolitical evolution occurring on the Central Northwest Coast. Archaeological and ethnographic data indicate that semi-sedentary collectors occupied the study region after ca. 3000 BP. Sx&barbelow;wóx&barbelow;wiymelh was occupied primarily between 2500 and 2000 cal BP. I evaluate whether our current understanding of Northwest Coast society after 2,400 years ago is reflected by the new data from the Sx&barbelow;wóx&barbelow;wiymelh pithouse settlement. My inferences are based on lithic, faunal, and botanical remains; radiocarbon dates; house and household size estimates; inter-house spacing; and village layout. Sx&barbelow;wóx&barbelow;wiymelh data document that the well-known Northwest Coast pattern of hierarchically organized households competing for prestige and social ranking did not necessarily emerge at the same time as the first aggregated settlements. Instead, it appears that this competitive social structure arose after 2000 cal BP. My analyses also show that low-mobility, multi-family households resided in pithouses almost year-round at Sx&barbelow;wóx&barbelow;wiymelh and may have been organized as village-scale corporate groups. The evidence confirms that several other salient attributes of ethnographic-era Northwest Coast society emerged about 2,000-3,000 years ago. These include control over access to important resource locales, aggregates of lineage-based multi-family households, and the capacity for co-resident households to coordinate their labors to perform complex tasks, such as mass-harvesting salmon. I also examine the relationship between community organization and ecological conditions. Warmer conditions marked by lower rainfall and frequent fires after 2400 BP played a significant role in the establishments and abandonments of many Sx&barbelow;wóx&barbelow;wiymelh houses in the region. I compare my findings to models of aggregation in the American Southwest and in the greater Pacific Northwest. The data are consistent with these models, showing that aggregation at Sx&barbelow;wóx&barbelow;wiymelh likely took place in response, at least in part, to climate change and was accompanied by labor shifts and by village-level control over access to key subsistence resources.