The foundation for Presbyterianism was laid by John Knox and John Calvin during the Protestant Reformation. The Presbyterian Church (USA), was founded in 1983 and was the result of the reuniting of two Presbyterian churches that had split during the Civil War period. It is the largest Presbyterian denomination in the United States. The Book of Order contains the PC (USA) form of government, worship guidelines, and rules of discipline. It has emerged as theologically more liberal than other Presbyterian organizations.