The answer is 50-52. Here is a selection from D. James Kennedy's and Jerry Newcombe's What If The Bible Had Not Been Written? This is from the chapter on the Bible and the founding of America.

        The late Dr. M.E. Bradford of the University of Dallas, author of A Worthy Company, has documented that fifty to fifty-two of the fifty-six men who signed the Declaration of Independence were Trinitarian Christians, men of good standing in a local, orthodox church. Of the fifty-five men who signed the Constitution, again he found in his research that fifty to fifty-two were professing orthodox Christians. Remember this the next time your hear that most of them were Deists. William J. Federer, editor of America's God and Country, summarizes the Christian affiliation of the writers of the Constitution: "29 were Anglicans, 16 to 18 were Calvinists, 2 were Methodists, 2 were Lutherans, 2 were Roman Catholic, 1 lapsed Quaker and sometimes Anglican, and 1 open Deist—Dr. Franklin who attended every kind of Christian worship, called for public prayer, and contributed to all denominations." Many of these men were trained in the leading colleges of the day   virtually all of which were evangelical Christian colleges.
 

To learn more about our Christian heritage, see the books What If Jesus Had Never Been Born? (press here to order the book) or What If The Bible Had Never Been Written? (press here to order it)
 

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