Final answer:
Alan Lomax discovered Muddy Waters in Clarksdale, MS while recording blues musicians for the Library of Congress in 1941. Muddy Waters became a pivotal figure in the development of blues music.
Step-by-step explanation:
The person who discovered Muddy Waters in Clarksdale, MS, was Alan Lomax. Alan Lomax was a musicologist and folklorist who worked for the Library of Congress, and in 1941, he made a series of field recordings of various blues musicians. It was during this trip that he recorded Muddy Waters for the first time. Muddy Waters, whose real name was McKinley Morganfield, later moved to Chicago and became one of the most famous blues musicians of all time, thus Lomax's discovery proved to be quite significant for the history of music.