Jazz is a distinctive stylistic influence in twentieth-century American organ music. Organ music in the United States during this period may be classified into four diverse categories: German-influenced; French-influenced; program music; and new styles that include twentieth-century techniques, such as serialism, chance (aleatoric), atonality, and jazz. The organ is an ideal instrument for jazz performance since the organ can provide diverse timbres, such as reeds (clarinets, trumpets, and trombones), strings (violin, viola, and cello), and overtone-rich sounds from mutations and mixtures.This document presents an analysis of jazz elements in twentieth-century American organ works, especially focused on the following selected organ works: Charles Ives' Variations on "America" (1891), William Albright's Sweet Sixteenths: Concert Rag for Organ (1975), and William Bolcom's Sometimes I Feel, and Free Fantasia on "O Zion Haste" and "How Firm a Foundation" from Gospel Preludes, Book IV (1984). The first chapter introduces jazz, including its definition, historical background, and styles. The next four chapters discuss brief biographical material, musical styles, compositions of each composer, and comprehensive musical analysis of their selected organ works, including form, melody, harmony, rhythm, timbre, and registration.