WMU doctoral dissertations are all available, full-text, in the Dissertations & Theses database.
If you search in the advanced search in Library Search, you may also find print copies of both WMU master's and doctoral dissertations that are available for check.
Try the following search:
1st box type: "African Americans"
2nd box type: "western michigan university"
3rd box type: thesis
Should you find a dissertation that is NOT full-text in the database, you can request it through Interlibrary Loan. About half of the colleges and universities in the U.S. will lend their theses, so you have a fifty-fifty chance of getting it.