Why did many people coming to the United States and Canada hundreds of years ago settle along costal plains and rivers

Western sahara is occupied by whom? a. mauritania b.algeria c. morocco d. tunisia

According to george washington, what was one reason a president should veto a bill?

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.