The influx of Spanish, Russian, and then American colonists into Alta California between 1769 and 1834 challenged both Native and non-Native people to reimagine communities not only in different places and spaces but also in novel forms and practices. The contributors to Forging Communities in Colonial Alta California draw on archaeological and historical archival sources to analyze the generative processes and nature of communities of belonging in the face of rapid demographic change and perceived or enforced difference.