How did changes in transportation and communication alter the economic landscape during the first half of the nineteenth century?

Why was the united nations established

Brainliesttt ! : ) -global military, political, and psychological responses to terrorism?

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.