The Nile river had a big impact on trade because it served as a source of transportation. Communities formed along the Nile were more developed.
Salt from the desert was a reliable and profitable resource traded.
Savannas were used to grow crops and the excess from the crops were traded.
Johnson announced that he would not run for a reelection, and that's when Humphrey decided to run, launching his campaign for presidency right after. Considering that he was loyal to Johnson's administration policies considering the Vietnam War, his own party disliked the idea of him running and they opposed to it, since they disagreed on how Johnson was dealing with it all.