What geographic feature made early americans consider isolation poloicies

Having fertile agricultural land on the Atlantic coast
having the rocky and Appalachian mountains as shields
having a large ocean on each side of the country

Ghana, first of the great medieval trading empires of western africa (fl. 7th–13th century). it was situated between the sahara and the headwaters of the sénégal and niger rivers, in an area that now comprises southeastern mauritania and part of mali.