The answer is <em><u>Popular Sovereignty</u></em>.
Spain's motivation to help the American colonists was driven by a desire to regain the land it had lost to Britain and, with other European powers, make incremental gains against British possessions in other parts of the world. ... In April 1779, Spain committed to helping the Americans.
1. Maine would come into the country as a free state
2. Missouri would enter the country as a slave state
3. Slavery would be banned above the 36°30 line and allowed below it
The Pony Express improved written communication
Answer:
Technology and improved transportation sent new products to markets across the U.S.