3)The Kansas Nebraska act.
The Kansas Nebraska act was made because the current states couldn't decide if new states coming into the union should be free states or slave states. The Kansas-Nebraska act set up Kansas and Nebraska as states and allowed them to vote on the issue.
Germany, Austria-Hungary, Russia i remember this from last years history :D
Air conditioning--with very hot temperatures, Americans preferred to stay in the northern states. Air conditioning convinced many to move South.
The South offered rich nature and industries thriving in particular oil. However, many Americans did not want to live in the hot conditions of the South. Air conditioning created an added appeal to live in the Southern states in particular Texas, Arizona, and New Mexico.
