These legendary blues pioneers are in a roughly chronological order starting with the earliest:
Charlie Patton
Charlie was the first well-known blues guitarist and singer. Born in 1891, he and fellow musician Willie Brown set the standards for many blues players that were to follow. Pony Blues and Oh Death are some fine examples of his work.
Eddie James "Son" House
Refined the bottleneck slide style of acoustic guitar into a style that defined the Mississippi Delta blues. An ordained Baptist preacher, House straddled the line between debauchery and holiness. Classics include: Preachin' the Blues and Rochester Blues
Robert Johnson
The liquor-loving Johnson is surrounded by legend. Reportedly selling his soul to the devil in exchange for unsurpassed musical talent, he died at the age of 27 howling  like a dog on his hands and knees. Too many hits to list but I Believe I'll Dust My Broom and 32-20 Blues stand out for me
Muddy Waters (McKinley Morganfield)
One of the first blues artists to make the transition from acoustic to electric guitar.
His Chicago blues band saw a literal Who's Who of blues legends pass through it. Please listen to You Got To Take Sick And Die Some Of These Days and
I Be's Troubled from his 1941 Library of Congress recording by Alan Lomax.
Willie Dixon
Wrote many of the blues standards of the day and was staff producer for Chess Records. Composed many of the blues hits of the 50's and 60's including two monsters-Back Door Man and Spoonful
Bo Diddley (Ellas McDaniel)
Heavily influenced by muddy Waters, Bo Diddley was a songwriter and singer. But he will be most remembered for the awesome playing of his own homemade guitars. He is regarded as one of the founding fathers of rock and roll music, a natural extension of blues music. Before You Accuse Me, Dearest Darling and Pretty Thing are tracks you have to listen to.