What makes someone an insider or an outsider? My dissertation investigates how early modern Amsterdammers came to understand themselves as belonging to (or being excluded from) communities in the city. Seventeenth-century Amsterdam was home to thousands of migrants, merchants, and free and enslaved Africans. In this distinctive city, slavery was technically illegal but tacitly allowed; women, especially migrant women, served as economic actors without male oversight; and middling merchants were among the only people in continental Europe for whom upward social mobility was genuinely possible. The success of a slave seeking freedom, a woman seeking independence, or a merchant seeking riches all depended on the same thing: whether they were considered an insider or an outsider to the community. I will analyze notarial documents, court records, diaries, and maps to determine how these Africans, migrants, and merchants constructed their communities. I will use interdisciplinary approaches to challenge traditional ideas about the development of imperial cities. My conceptual framework draws on social exchange theory, a theory developed by sociologists to interpret the transactional nature of human relationships. I will also compare seventeenth-century maps to geographic models of urban development. This analysis will show how the city's physical geography affected its social landscape. Combining these approaches with perspectives from cultural and economic history, I will examine notarial testimonies, first-person accounts, and court records from the seventeenth century. These sources illustrate how Amsterdammers exchanged goods and ideas, drew up agreements, and prosecuted deviants. These interactions helped to establish and police the boundaries of belonging. Studying these archival sources will reveal the potentially staggering rewards and consequences of inclusion or exclusion. I hope to show how small-scale interactions had large-scale impacts, as communal ties shaped the city at the heart of a global empire.