Final answer:
In jazz history, the 'Southwest' most commonly refers to the Southwest United States, a region with a significant contribution to the development of jazz.
Step-by-step explanation:
In the context of jazz history, the term 'Southwest' often refers to the Southwest United States, which has been influential in the development of certain styles of jazz. The region has its own distinct cultural contributions to the genre, notably from states like Texas, which has produced notable jazz musicians and has a rich history of jazz performance and evolution. When examining the history of jazz, it's important to consider the various regional influences that have shaped the music, and the Southwest United States is certainly a part of that mosaic.