Black churches are an important topic in the context of Black heritage, and they definitely deserve categories within the umbrella of African-American history and heritage.
I think much of the history of black churches in the context of African-American history is strongly associated with the African-American denominations with which most (but not all) of the local churches are affiliated. The Wikipedia category Historically African-American Christian denominations provides a decent road map for getting started on sorting these denominations. There are a few WikiTree categories for African-American denominations (disclosure: I created some of them) within the Religious categories. See, for example, Category:African Methodist Episcopal Church, which includes a very short free-space page for one specific local church/congregation, as well as a well-populated subcategory for AME ministers. There are WikiTree categories for at least two other "African" Methodist denominations within the Methodist Denominations category and there's one for the Church of God in Christ (but the COGIC category description doesn't mention the denomination's African-American identity). However, I don't think there are any categories yet for the National Baptist Convention, much less the other denominations that I'm not as familiar with.
I think the Black denominations and churches should have an umbrella category in the African-American category structure (maybe with a title conveying the meaning "Historically Black Religious Institutions"), and that local Black churches like Greenwood No. 1 Baptist could be categorized in their local communities and also in denominational categories (if they are affiliated with a denomination) or in some sort of "Other Black Churches" category within "Historically Black Religious Institutions".
