Christian Universities Online explains that the history of Christian universities in the United States dates back to 1636, with the opening of Harvard University who had a founding rule stating that all students should know God and Jesus Christ and for Him to lay the foundation for their education. While today, Harvard is more diverse in its acceptance of a student and their religion; many institutions were founded as a Christian university. The history includes universities such as Brown, Yale, and Princeton.
Currently there are 3.4 million students enrolled in private universities. The graduation rate at a private institution is 30% higher than public, but the cost is also more than double.
The following graphic is an interesting outline of the Christian universities in the United States:
Source: http://www.christianuniversitiesonline.org