What factors contributed to the westward expansion of the U. S.? the Revolutionary War
the quest for land, wealth, and adventure
the Cold War
the discovery of gold
the Homestead Act
increased immigration

im pretty sure its :The quest for land,wealth and adventure, The discovery of gold, the Homestead Act, and increased immigration

i hope I remembered right :)

Explanation:

i think it would be reparing roads  

answer:

it caused mass african migration, african populations to grow, african empires to topple, and racism against slaves to emerge.