According to the Encyclopedia of Freemasonry, Thomas Webb and William Preston are generally credited with formulating the Most Excellent Master Degree based on a series of lectures. The MEM Degree was adopted into the American Rite of Royal Arch Masonry in 1854. Of course, this is a VERY summarized answer, but hopefully will sufficiently address the question.
According to the Encyclopedia of Freemasonry, Thomas Webb and William Preston are generally credited with formulating the Most Excellent Master Degree based on a series of lectures. The MEM Degree was adopted into the American Rite of Royal Arch Masonry in 1854. Of course, this is a VERY summarized answer, but hopefully will sufficiently address the question.