The Dixieland sound is a mixture of musics including Marches from John Phillips Sousa and Ragtime (1850s). Sousa's parents were from Portugal and Bavaria (Germany), where the Tuba was invented. Marches were commonplace in Germany in the 1700s and 1800s, especially in classical music by Wagner, Mozart, Beethoven and others; and also in the military to assist in transportation of troops from one place to another. Sousa was heavily influenced by this music, and his marches have become quite famous in the world of Dixieland and origins of Jazz (1920s USA), and Swing (1930s USA).
The rest is history.