This book centres on Roger Barlow: merchant, explorer, ally of Sebastian Cabot, supporter of Thomas Cromwells vision for Wales, proponent of expanding English trading routes, and the first Englishman to write a detailed eyewitness account of America (included in A Brief Summe of Geographie). It investigates the early lives of both men and the family-based guild networks that brought Barlow from Colchester to London, Morocco, and on to Seville where Cabot was Pilot Major. There, Barlow joined other English merchants in supporting voyages and supplying Castiles Atlantic settlements. From 1526 to 1528 Barlow joined Cabot in an exploration of the upper reaches of the Rio de la Plata river system, becoming the first Englishman to set foot in Argentina, Uruguay, Paraguay, and Brazil. When both men returned to the British Isles, Barlow around 1531 and Cabot in 1548, they had trading, navigational, and exploratory knowledge that made them truly unique. In tracing Barlow and Cabots circle from the mid-fifteenth-century Mediterranean to the burgeoning Iberian Atlantic of the sixteenth century, and then back to Reformation England and Wales and to a merchant elite just beginning to look at extending its trading reach into the Atlantic and beyond, the book constitutes a critical contribution to the emerging fields of Atlantic and global history. It examines how shared knowledge as well as the accumulation of capital in international trading networks prior to 1560 influenced emerging ideas of trade, discovery, settlement, colonization, and race in Britain.