From his official site - a short portion of Muddy Waters' bio:
He was born McKinley Morganfield-Muddy Waters is a nickname given him in childhood-in the tiny hamlet of Rolling Fork, Mississippi, on April 4, 1915, but from the age of three, when his mother died, was raised by his maternal grandmother in Clarksdale, a small town one hundred miles to the north.
It is scarcely surprising then that the Delta region has nurtured a tradition of blues singing and playing that reflects the harsh, brutal life there, a music shot through with all the agonized tension, bitterness, stark power and raw passion of life lived at or near the brink of despair. Poised between life and death, the Delta bluesman gave vent to his terror, frustration, rage and passionate humanity in a music that was taut with dark, brooding force and spellbinding intensity that was jagged, harsh, raw as an open wound and profoundly, inexorably, moving. The great Delta blues musicians-Charley Patton, Son House, Tommy Johnson and, especially in Waters' case, the brilliant, tortured Robert Johnson-sang with a naked force, majesty and total conviction that make their music timeless and universal in its power to touch and move us deeply
Growing to manhood there, in the very heart of the region that had spawned this magnificent music, Waters was drawn early to its stark, telling, expressive power. He had been working as a farm laborer for several years when at thirteen he took up the harmonica, the instrument on which many blues performers first master the music's rudiments. Four years later he made the switch to guitar. "You see, I was digging Son House and Robert Johnson." The two were the undisputed masters of the region's characteristic "bottleneck" style of guitar accompaniment. With this technique the Delta bluesman could utilize the guitar as a perfect extension of his voice, the sliding bottleneck matching the dips, slurs, sliding notes and all the tonal ambiguity of the voice as it is used in singing the blues.