Lili Boulanger was an important composer of early twentieth century French music. Her compositional style represents a development and mastery of musical techniques of the great composers of her time including Fauré, Debussy and Wagner combined with her own creative expression. The result is a compelling musical language that was uniquely her own. She held an important place among her contemporaries in Paris and her accomplishments were considered newsworthy during her lifetime (1893- 1918). She obtained a much sought-after publishing contract with Ricordi. Her more famous sister, Nadia Boulanger, felt that Lili was the better composer of the two, and her peers and music professors clearly felt that both her musical and personal qualities were extraordinary. Evidence of her intelligence, creativity, and artistic growth can be seen in her music. As the first woman to win the Prix de Rome (July 5, 1913), Lili Boulanger, unlike Clara Schumann, Fanny Mendelssohn, or Alma Mahler, was acknowledged and acclaimed during her lifetime for her skill as a composer. Yet, nearly a century later the music of this talented French composer is not as well known as it deserves to be. In an effort to discover the reasons for this relative anonymity, this document will examine Lili Boulanger's life including her family and childhood influences, musical training, preparation for the Prix de Rome and the influence of Claude Debussy and other composers. This document will discuss her mature compositional style, specifically as it is reflected in her song cycle, Clairières dans le ciel. The text will be examined in conjunction with the literary movement of symbolism in 20th century France and the symbolist poet, Francis Jammes, with special attention to the composer's personal identification with the poetry. Considerations of the musical setting of the cycle will include the melodic style as it relates to the text, the harmonic idiom and its relation to the poetry, rhythmic and metrical devices used, formal devices and the relationship of the piano accompaniment and the voice. Performance considerations for this cycle include the recommended transpositions if performed by soprano rather than the tenor voice for which it was originally composed and the level of difficulty from an interpretative as well as technical standpoint.