Thanks for your question. It is such an impossibly huge question, the birth of soul, you could take it academically in dozens of directions. In a very general sense, realize the intersections of black/white gospel, blues from various regions, tin pan alley, jump-blues, jazz of varying styles and regions, country music, doo wop, country & western. Here are a few articles to consider and a couple books:
One big problem you’re probably running into is research that falls into the “nonacademic” category. Collectors, bloggers, Rolling Stone-level musicology. This isn’t very helpful for a college-level paper. Musicologists and cultural anthropologists have yet to create a sizable body of work that explores the cultural tradition and history of soul music. Basically, it’s not a paper you can write in a weekend as you need to take time to read and absorb many snippets of information, verifiable or not. I’ve been “studying” it for a long time and I’m still trying to understand.
WHATEVER YOU DO, please don’t reduce your paper to Motown, Stax and Hi records. It’s so much greater than that.