The Dutch presence on the Río de la Plata in the mid-seventeenth century cannot be fully understood without a discussion of the commercial links the city of Buenos Aires had established since late in the sixteenth century with the Alto Peruvian provinces; the provinces of Tucumán, Cuyo, and Paraguay; and Spain, Brazil, and Western Africa. The trading networks that connected Buenos Aires to Potosí linked the urban centers in the governorships of Tucumán and Río de la Plata and brought silver to the seaport and, to a lesser extent, the commodities needed to engage in commerce in the South Atlantic. Complex networks of trade and credit integrating this broad space converged in Buenos Aires, despite the multiple attempts on the part of the crown to limit the role of Buenos Aires, a competitor to Lima. Stimulated by Spanish legislation, but primarily in violation of it, merchants, commodities, and financial instruments continued linking the regional economies that lay between Buenos Aires and Potosí to the Atlantic throughout the seventeenth century. This chapter reviews the Spanish policies that encouraged the growth of trade through Buenos Aires and the changes in international policies and politics that affected the Río de la Plata. The focus is not just on direct trade in slaves and merchandise into Buenos Aires, but also on the mechanisms that legalized that trade and made possible its transshipment inland.