The American Enlightenment preceded the American Revolution and lasted into the early nineteenth century. It took root due to a variety of influences and factors.
Firstly, the Americans were influenced by European Enlightenment thinkers such as Voltaire, Adam Smith, Montaigne, David Hume, and Jean-Jacques Rousseau. Ideas common among the European Enlightenment thinkers included a commitment to reason over superstition and a championing of individual liberty. Both of these tenets challenged the absolute authority of monarchies and the Roman Catholic Church, both of which had dominated supreme in the Middle Ages. The European Enlightenment had its genesis in the seventeenth century and was ongoing into the eighteenth. Prominent Americans at the time were familiar with Enlightenment ideas discussed in continental salons, so these ideas were brought into the country that way.
Secondly, the revolutionary sentiments within the colonies (incited by dissatisfaction with the English government) made Enlightenment ideas more popular. Emphasis on individual liberty, religious freedom, and republicanism were major elements of the revolutionists' thinking at the time. These ideas all had roots in Enlightenment ideas. The American Enlightenment was also influenced by the organization of Native American governments with whom the American colonists came into contact. The Iroquois Confederacy was one such alliance, a union between several individual tribes that inspired the likes of Benjamin Franklin and Thomas Jefferson.