The "primaryness" of a source emerges in relation to the researcher's engagement with it. The UC Berkeley Libraries define primary sources as "either created during the time period being studied or...created at a later date by a participant in the events being studied (as in the case of memoirs)."
(source: Finding Historical Primary Sources: Getting Started, last updated 8/12/18, http://guides.lib.berkeley.edu/c.php?g=4409&p=15606)
When determining primary sources for your research, it's helpful to give yourself a historical context that defines your search. This could be a range of dates. It could also be determined by geographical sites of origin. You might also be interested in a specific type of source. Some examples include:
Databases and digital repositories can offer a multitude of paths to potential primary source material for your research. In addition, you might want to try searches in the CLIO catalog, limited by date of publication.
Contains over 1,200 plays by 300 playwrights from North America, Africa, the Caribbean, Europe, Australia, and other locations, including some of the great names in drama (Zora Neale Hurston, August Wilson, Ossie Davis, Sonia Sanchez, Langston Hughes). Also included, selectively, are production photographs, as well as images of playbills and other ephemera. Many of the plays are previously unpublished.
"A fully cross-searchable gateway to Black Studies including scholarly essays, recent periodicals, historical newspaper articles, reference books, and much more. It combines essential resources for research and teaching in Black Studies, including The Schomburg Studies on the Black Experience, Index to Black Periodicals Full Text, Black Literature Index, and the Chicago Defender historical newspaper from 1912-1975."