This dissertation examines how people in two seventeenth-century cities – Amsterdam and New Amsterdam, which later became New York – navigated the challenges of migration, belonging, and community construction. Drawing on notarial records, court documents, epistolary sources, and administrative papers, I trace a path of migration from the streets of Amsterdam to the fields of New Netherland. I argue that transatlantic migration was a key component of community-building. I introduce the idea of strategic mobility as a means by which free Black Africans in Amsterdam coped with the difficulty of life on the margins of society in Europe. By putting maritime migration at the center of my analysis, I reveal how the structure of seafaring life shaped communities on land. Using the rich notarial records of the Amsterdam City Archives to excavate and reconstruct the experiences of maritime migrants, I show how they used urban spaces to transform land-based lives into ones ready for seafaring. Re-conceptualizing the transatlantic journey as one that began at home or in a notary’s office, I reveal how migrants transferred, translated, and transcribed their private lives into the public record. I argue that migrants instrumentalized their relationships, debts, and obligations as they confronted the risk of death or loss at sea. Moving ashore in America, I investigate the racialized social economies of Anglo-Dutch colonies, revealing how enslaved people – particularly enslaved women – countered and circumvented their systematic exploitation.