For historical information that isn't a primary source, you can use secondary sources. Secondary sources are works that analyze, assess or interpret a historical event, era, or phenomenon. Unlike primary sources, secondary sources are written well after the historical event/era/phenomenon takes place. For example, a book published in 2020 analyzing the effects of the women's movement during the Progressive Era on American society is considered a secondary source.
Secondary sources can be articles, books, videos, etc.