The conversion efforts of European Christian missionaries, both Catholic and Protestant, in the Americas during the 16th, 17th, and 18th centuries form a single, continuous thread. From Columbus to the Puritans and beyond, Europeans arriving in the Americas virtually always included in the justification of their colonizing efforts the desire to convert the native peoples to Christianity, as their ancestors had been converted centuries earlier. These essays not only explain how vital these conversion efforts were to European expansion but also explore the effects of such conversion work on the Protestant Reformation that was raging in Europe.