In surveys of American architecture, the so-called “colonial period” from the founding of Jamestown in 1607 to the war for independence in the 1770s has generally been viewed from an “Anglo-American” perspective with a concentration on the British colonies that would become the United States. This period has been defined by the transplantation of architecture from the “mother country” to British North America according to what the architectural historian John Summerson has characterized as “English standards pure and simple.” The persistence of historiographical assumptions that privilege English sources and focus on evidence of “Englishness” still serves as the core of early American architectural narratives. While an effort has been made to increase the diversity of those represented, yet one dimension has essentially been written out, that of America’s connection to Ireland. And yet Irish elements have long had a presence in the already existing historical evidence. Therefore this dissertation takes an alternative view of that same colonial history by collecting the available Irish materials and tracing the threads that tie Ireland to America, whether that connection is direct or mediated through England. By assembling various forms of evidence, often relegated to footnotes, asides, or ambiguous citations, this dissertation seeks to construct a counter-narrative that spans the Atlantic and stretches from the 1530s to the 1730s. It explores a diverse constellation of elements including landscapes, plans, buildings, and monuments, while situating them within a larger historical context, thereby reframing some of the same canonical events, individuals, and artifacts that currently appear in surveys of American architecture. With a shift in perspective comes a shift in the history, one that complicates, challenges, and at times upends, Anglo-centric readings of colonial America and the transformation of its physical environment. For when seen from the perspective of Ireland, a more complex, as well as a more “Irish,” story emerges, resulting in a history that has, in effect, been hiding in plain sight. In making this history visible, the dissertation addresses both the historical and historiographical conditions that produced some of the gaps, tensions, ambiguities, and erasures that have contributed to keeping this history hidden. Taking Summerson’s Architecture in Britain, 1530-1830 as a starting point, the dissertation begins in 1530 and examines some of the preconditions for American colonization in England and Ireland. Then, working from the historiographical foundations already laid regarding the English plantations in Ireland and Virginia, it goes on to address the continuity of connections that run through New England, the “Middle Colonies,” and the American south, including such well known works as William Penn’s plan for Philadelphia, George Berkeley’s Whitehall, and William Byrd II’s Westover, all three of which have been viewed as exemplary in their ties to English sources and influences. Though traditionally divided by period, type, style, and region, here they are no longer treated as isolated data points but rather as part of a larger, inter- connected, and continuous story, one intimately, and inextricably, tied to Ireland and “Irish” networks in England and America. In addition, by examining the historiographical as well as the historical dimensions and placing the history and the historiography in dialogue, this dissertation hopes to offer insights into the production of early American architectural history, as well as the production of plans, spaces, and objects. In doing so it seeks to call into question the overwhelming “Englishness” of the American colonial period as it has been constructed through histories of American architecture and planning during the twentieth-century.