The "discovery" of future USA by Europeans laid the groundwork for the vast number of Christian denominations in existence today. At this point in history in Europe, there was one church, the Catholic Church. (Several tiny groups of Christians existed who had separated from the Catholic Church, but were in hiding.) The 1500's experienced the Protestant Reformation: by the end of the 1600's five different Christian groups existed in Europe (Catholic, Lutheran, Anabaptist-related, Church of England, and Calvinist/Reformed). If Christianity had stayed in Europe it would have remained around that number. That changed when Christianity came to America, and mainly because of one difference: the vast amount of land in America. This is why: Europe was settled and, therefore, when these new groups formed during the Protestant Reformation, they had to carve out an area of previously held Catholic-land. But in American colonies, you could simply move to a new area and begin a new faith. That is exactly what Roger Williams did in the mid-1600s: the Puritans did not like his teachings in Massachusetts, so he simple moved beyond their control and started a Baptist church. Multiply that times many people with many different ideas about Christianity and a huge uncharted territory (USA) to expand in, and it equals a large number of Christian denominations in this new America. For a more detailed explanation, go here.

The forced conversion of Native Americans came from the Spanish Catholic branch of Christianity. This occurred for two reasons, which are interrelated. First, when the Spanish Catholic explorers came to the "New World," they claimed land as part of Spain. In essence, these lands were now an extension of Spain. Second, Spain (which were going through the Protestant Reformation) strongly encouraged (even in some places of using the Inquisition) people to remain Catholic. So it was important to be Catholic if you lived in Spain. Tie these two together, and the result is that whenever new land was added to Spain, the inhabitants needed to become Catholic. Therefore, the Native Americans now lived on Spanish land (according to the mindset of the explorers) and so needed to become Catholic.

The First Great Awakening (1GA) helped spawn the American Revolution. Prior to the 1GA, the colonists did not view themselves as a unit, as a whole. Instead they were part of a colony or some other social or religious group. But the 1GA was the first mass movement which was felt (positively or negatively) throughout the colonies. It was the first time that colonists from Georgia to New England had a shared experience. In addition, the 1GA helped to introduce emotionalism and of the importance of following acting on your personal emotions. These two would be needed thirty years later as the colonists had to become angry together and decide to act together in order to break from the rule of England.

Evangelicalism can be defined as the acceptance of the Bible as the sole authority for the Christian, the need to experience a conversion, emotionalism, and the need to share Jesus with others (evangelize). With this definition, Evangelicalism began in the First Great Awakening.

Whereas the First Great Awakening (of the 1700s) began in the urban areas and moved to the frontier, the Second Great Awakening (2GA) began in the frontier of the West (meaning Kentucky and Tennessee) and moved to the urban east. The 2GA was different than the 1GA in a number of other ways: use of camp meetings, more pronounced use of emotions (crying, running, rolling, barking, shouting, etc.), introduction of the anxious bench (Charles Finney; precursor to the altar call of today), increased conversion of slaves, use of large tents, rise of the Baptists and Methodists, and proliferation of societies (volunteer organizations whose purpose was to improve society; for example, Temperance or restraining from drinking alcohol which would eventually lead to Prohibition). One gradual change which fully occurred at the end of the century: a movement toward directing services so that people were brought to a state of spiritual crisis instead of waiting on God to direct it.

Many people became Christian during the Second Great Awakening. Combine this with the idea of a new nation with very little restrictions or laws governing many aspects of a person's life, and you end up with Societies. Many Christians looked around at their new country and decide to improve different aspects by forming Societies. Examples of Societies include abolition (free slaves), temperance (reduce alcohol consumption), missions, education, Sabbath observance peace, prison reform, Sunday school, and women's rights organizations. These will have varying degrees of success. For example, the Temperance Movement will eventually help lead to Prohibition and the decision by some denominations to switch from wine to grape juice during Communion. (To learn more about this, go here.)

The 50 years after the Civil War experienced many innovations which American Christianity would struggle with: the issue of evolution and geological studies questioned the Genesis account of creation, higher criticism of the Bible questioned the validity of some biblical stories and concepts, the rising fields of sociology and psychology questioned the spiritual aspect of humans and reduced religion to a social phenomenon, and comparative religious studies questioned the validity of Christianity as the sole method for reaching God.