On July 13, 1910, Mary Lou Williams was born Mary Elfrieda Scruggs in Atlanta, Georgia — and began playing professionally at seven, becoming one of the most consequential figures in American jazz history while remaining one of its least celebrated.

Williams was a staff arranger for Andy Kirk's Clouds of Joy orchestra throughout the 1930s. She wrote and arranged the charts that made Kirk's band a leading swing ensemble, without receiving commensurate billing or pay.

By the 1940s she had moved on. She became the only musician to have personally participated in every era of American jazz from swing through bebop through free jazz — playing and composing in each, known and mentored by Dizzy Gillespie, Charlie Parker, Thelonious Monk, and Miles Davis. She tutored Monk in advanced harmony during a period when his reputation was not yet established.

She converted to Catholicism in 1954, largely stopped performing for three years, and returned. She wrote three jazz masses performed at St. Patrick's Cathedral. She was appointed to the faculty at Duke University in 1977.

She composed the Zodiac Suite in 1945, a landmark work that synthesized jazz, classical form, and spirituals — premiered at Town Hall in New York to critical acclaim and subsequently ignored for decades.

She died in 1981.