How did the development of an urban, industrial society exacerbate inequalities in the u. s society and promote class violence?

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.

What notable contributions to science has sandia national labs (snl) produced over the years?

Mee why did the government control the news and information americans received about the war? to eliminate propaganda that unfairly targeted immigrants to influence public opinion in support of the war effort to inform americans about troop movements and major battles