Lugenia Burns Hope helped form the Neighborhood Union, which organized African Americans who worked for white employers.
promoted integration of white and African American neighborhoods.
promoted health and education in African American neighborhoods.
organized African Americans to fight for their voting rights.

Why is it useful for historians to base certain studies on the analysis of historical periods

The rise of advertising in the 1920s. i am good with seeing how advertisements shape the roaring twenties and how it developed a new way of life through modern days. but i am not sure what the details of advertising in the 1920s were. if possible can you send me links (preferrably credential links) to sources that maybe show like the first company to start advertising through the radio, how advertising benefits (statistics graphs), etc.

Why did the outbreak of world war 2 create a need for new military bases across the country?