San Juan Island sites (N = 65).

Recent developments in radiocarbon dating have enabled archaeologists to re-examine the question of population dynamism in the Salish Sea. This study expands on Taylor and colleagues (2011) using Kernel Density Estimation (KDE) and an expanded data set of 538 radiocarbon dates from academic and cultural resource management literature. The expanded sample suggests a pattern of population growth from 3200–2800 cal BP in coastal Northwestern Washington, with population growth in the San Juan islands during 2600–2200 cal BP. A subsequent decrease in radiocarbon frequencies and large sites suggests shifts in use of the San Juan Islands, followed by peak large-scale occupation from 650–300 cal BP. This pattern is robust whether marine or terrestrial dates are considered. However, marine dates are less sensitive to questions at smaller temporal scales. The broad scale radiocarbon frequency patterns observed are also consistent with those observed in southwest coastal British Columbia (Ritchie et al., 2016; Morin et al., 2018).