I'm a bit anxious about posting this, but I foresee it becoming a technical issue, so here it is! I know how heated debates about proper grammar can get, so I want to emphasize that what I'm posting here is an overview of different positions and not an invitation to start arguing angrily about which is worse. Let's be civil :) (And in case anyone is worried, this is a grammar discussion, not a "PC thing.")
Hyphens can be very confusing. It's hard to know when to use them and when not to. As a society, I feel like we're trending toward dropping hyphens even in circumstances where they have a positive grammatical impact. In most cases, grammarians have developed clear and indisputable rules about the usage of hyphens, but that's not exactly true for proper nouns and adjectives.
Years ago, noun phrases like "African-Americans," "Chinese-Americans," etc. used to be hyphenated. So you might have said something like "A lot of Chinese-Americans live in California," and you would not have been incorrect. Today, this is incorrect. It is widely accepted among grammarians that a hyphen should not be used in those noun phrases. As far as I can tell, this is not an issue that is being debated anymore. All of the experts agree on this. The correct form of the example sentence should be "A lot of Chinese Americans live in California," without any hyphens.
The problem is with adjectives.
If you google search "should african american be hyphenated" the first result is a 2012 post from the grammarphobia blog, which states "In the end, we (along with the editors at Random House) decided to hyphenate African-American ONLY as a compound adjective preceding a noun (as in "an African-American idiom"). We decided not to hyphenate it as a noun phrase (as in "African Americans" or "he is an African American")." This seems to make sense. The grammarist blog's official position is "When using the term African-American as a phrasal adjective preceding the noun it modifies (e.g., an African-American woman), be sure to include a hyphen. When the phrase functions as a noun or an adjective phrase following what it modifies, no hyphen is needed."
Similarly, if you go to the Wikipedia article for "African Americans," that noun phrase is not hyphenated, and the end of the first paragraph says "As a compound adjective the term is usually hyphenated as African-American." So there you go! ...But what about that "usually"?
The truth is, there is not a consensus on this. In fact, one of the most important grammar reference books in America--the Chicago Manual of Style--says that you should not use a hyphen in either case, noun or adjective. Their official reasoning can be found in this PDF: http://www.chicagomanualofstyle.org/16/images/ch07_tab01.pdf
Their rule for proper nouns and adjectives is "Open [not hyphenated] in both noun and adjective forms, unless the first term is a prefix or unless between is implied." Here are some of their examples: African Americans; a Chinese American; Middle Eastern countries; but the Franco-Prussian War; Anglo-American cooperation.
Not everyone likes this! But the Chicago Manual of Style is sticking with it. They were asked about it in a Q&A that you can read fully here: http://www.chicagomanualofstyle.org/qanda/data/faq/topics/HyphensEnDashesEmDashes.html?page=2
Someone said "I maintain that the examples 'African-American,' 'Asian-American,' and even 'Native-American' (or as I prefer, American-Indian) are all compound proper nouns and must be hyphenated. They are not merely Americans who happen to be African, but rather African-Americans--a distinct ethnic and cultural group. Irrefutable logic?"
Chicago Manual's response: "I don't see any logic in requiring the hyphenation of compound proper nouns when they are used as adjectives. In fact, because they are capitalized, there is no need for additional bells and whistles to signal that they belong together: Rocky Mountain trails, New Hampshire maple syrup, SpongeBob SquarePants lunchbox."
So...while the Chicago Manual of Style claims that you should never use a hyphen for "African American," the grammarist blog and many others say "be sure to include a hyphen" when it's an adjective!
Which one should you use, then? I asked myself this when I wanted to create a category for unconnected profiles of African Americans. Initially I felt like there should not be a hyphen for the adjective, but I did a quick google search to make sure I was right, and I was very surprised to see the top result say that I should use a hyphen. Then I found the Chicago Manual of Style's very comprehensive rebuttal of that, and I felt far more comfortable with their version. So there is now an "African American Unconnected Profiles" category--no hyphen included.
But what about future categories, free-space pages, biographies, and the like? Since there is no consensus among the experts, I imagine that people should use whichever they feel is appropriate. I'm not much of a tech person, but I'm guessing that the presence or absence of a hyphen is significant enough to throw off a computer--for example, G2G is suggesting I tag this post with "african-american" but not "african_american."
My impression is that WikiTree avoids taking an official stance when neither side is incorrect. For example, there has been a lot of debate about "USA" vs. "United States" vs. "United States of America" when it comes to location fields, but no version has been selected as the "official" one. In general, WikiTree encourages people to use whatever phrasing or grammatical style they feel comfortable with as long as a) it isn't provably inaccurate and b) it doesn't confuse people. I don't think this is necessarily ideal--my position would be to accept the Chicago Manual of Style's rule and use it on all of the American categories as an official guideline, to avoid confusion--but my dictatorial opinions haven't won over anyone on this site in the past, haha.
I didn't set up this post to start a debate; I set it up as a reference point so that if the issue arises in the future, people can refer back to it. Mostly, I just wanted to point out the significant fact that there is active disagreement among experts on this issue, so neither the pro-"African-American" people nor the pro-"African American" people can claim that the other version is wrong. As for which is more correct...that depends on your opinion. I will continue to use the non-hyphenated "African American" as an adjective, and you can use whichever you prefer! :) ...Just don't use it as a hyphenated noun. Because that's actually wrong! And if you see anyone on this site doing that and insisting it's correct, you can direct them to this post to clear it up.
If any sort of official policy discussion happens around this issue in the future, please comment with the link here!