Answer:
1:
A: The general trend of territorial acquisition is westward.
B: Since territorial acquisition did not happen gradually, rather in large chunks, state boundaries often occur at the borders of each acquisition. One example of this the Mississippi river, which has a lot of state boundaries on it, and was the west-most border of an acquisition.
2:
The Louisiana purchase occurred in 1803, and was a result of Napoleon's loss of Haiti. Without Haiti, the French had no use for the vast colonial lands in the Americas. It was sold to America. America was interested in it because they got a great deal on it, and the spirit of manifest destiny was beginning to form.