This dissertation examines the political origins of Loyalism in New York City between 1768 and 1778. Anchored by an analysis of political mobilization, this dissertation is structured into two parts. Part I has two chapters. Using a variety of private and public sources, the first chapter analyses how 9,338 mostly white male Loyalists in New York City and the counties of Kings, Queens, Suffolk and Westchester were mobilized. Chapter 1 argues that elites and British forces played a fundamental role in the broad-based mobilization of Loyalists in the province of New York. It also recognises that colonists signed Loyalist documents for many different reasons. The second chapter of Part I is a large-scale prosopographical analysis of the 9,338 identified Loyalists. This analysis was based on a diverse range of sources. This analysis shows that a majority of the province’s Loyalist population were artisans aged between 22 and 56 years of age. Part II of this dissertation examines political mobilization in New York City between 1768 and 1775. In three chapters, Part II illustrates how elite and non-elite white male New Yorkers coalesced into two distinct groups. Chapter 3 concentrates on the emergence of the DeLanceys as a political force in New York, Chapter 4 on their mobilization and coalescence into ‘the Friends to Liberty and Trade’, or ‘the Club’, and Chapter 5 examines the political origins of what became Loyalism by studying the social networks of three members of ‘the Club’. By incorporating an interdisciplinary methodology, Part II illustrates that members of ‘the Club’ developed ties with one another that transcended their political origins. It argues that the partisanship of New York City led members of ‘the Club’ to adopt inward-looking characteristics that affected who they interacted with on an everyday basis. A large proportion of ‘the Club’’s members became Loyalists in the American Revolution. This dissertation argues that it was the partisanship that they developed during the late 1760s and early 1770s that defined their allegiance.