Sir Humphrey Gilbert's 1583 expedition to North America was the first attempt by an Englishman to colonize beyond the British Isles, and yet it has not been subject to thorough scholarly analysis for more than seventy years. Although it is often overlooked or misinterpreted by scholars, an exhaustive examination of the voyage reveals the complexity and preparedness of this and similar early modern English expeditions. Gilbert recruited several specialists who expended considerable time and resources while researching and otherwise working in support of the voyage. Their efforts secured much needed capital, a necessary component of expensive private voyages, and they ensured that Gilbert had a reasonably clear picture of North American geography, flora, and fauna before leaving England's shores. Focusing specifically on the cartography, nautical science, and promotional literature of the expedition, my dissertation clarifies their role in Elizabethan colonization and elucidates the preparation stages of early modern English colonizing voyages. By enlisting promoters like Richard Hakluyt, Stephen Parmenius, and Christopher Carleill, whose skills and experience varied considerably but who nonetheless wrote compelling, well researched texts spanning multiple genres, Gilbert maximized his chances of gaining subscribers. He also recruited various skilled practitioners like John Dee to create manuscript and printed maps that helped him to gain permission for the voyage, to advertise it, to guide it, and to stake his claim to North America. Much of Gilbert's intelligence came from reading printed and manuscript texts, which allowed him to establish England's legal claim to North America. He and his supporters also interviewed Englishmen and foreigners who had been to Norumbega. Based upon their navigational research, Gilbert's circle intended to implement several seafaring advances during their transatlantic crossing, even if the crew was unable to execute all of their plans. Scholars typically depict England's earliest colonizing voyages as being haphazard and experimental in nature, but a close examination of the preparations for Gilbert's voyage shows that he and his supporters worked diligently for several years to ready themselves for their expedition to North America.