Christianity and American Freemasonry

What is it about Freemasonry that would cause Churches to forbid or openly discourage seventy million Americans from membership? Why have eight popes condemned the Lodge?
This book, which was first published in 1958 and the first full-length treatment of this subject by an American Catholic in 50 years, was written by William J. Whelan to explain why the Church has warned her sons against affiliating with the Masonic lodge since 1738.