How did American corporate interests influence U. S. imperialism over the turn of the twentieth century?

What enabled the drastic increase in us troop development to vietnam between 1964 and 1965?

Why are primary sources important when studying historical events

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.