A good obituary is a great source of information. You can use the two or three sources listed below, or Google your person's name followed by obituary.
Black Lives Matter
These groups and movements can all be researched, but the more recently they have occurred the more widely you will want to search. I'll demo how to research both the Black Lives Matter movement and the #MeToo campaign/movement to demonstrate how to search for "biographies of these types of groups.
These groups often have to be legitimized in some way and because of this are easier to search. They can be searched in online catalogues as you would search for people, by their name. You can add history to the search to see if there are focused works on these groups: American Red Cross history, for example.
You can also try searching in business databases for information on them. I've listed two below that might help.
To search for book-length, scholarly biographies about a person:
button or the link Request via Interlibrary Loan to order the book. Books will take about 7 - 10 days to arrive.