When was your speech first presented? One of the best places to get a sense of the time period is through newspapers. UNLV Libraries has a wide selection of newspaper databases going back centuries through today, including some specific African American historic newspapers.
You will be able to find a wide variety of rhetorical analyses & criticisms, along with a wide variety of resources about the speaker on the Library's QuickSearch (on the home page), in the library catalog, and in UNLV Libraries databases such as Communication & Mass Media Complete, Communication Studies, ComAbstracts, and JSTOR.
You may also want to try Google Scholar to expand your search to a wider variety of disciplines at once.