In the early 1800s, why was there so little settlement on the great plains?

Here’s the first one let me send the next page of the passage

Why did the 24th amendment and the civil rights act succeed when other legislation had failed?

Prior to the presence of europeans on the continent, the slave trade in africa a) did not exist in any form. b) was limited to internal trade only. c) included the trans-saharan and indian ocean slave trade. d) was rarely needed due to the lack of an agricultural economy.