1. The first sizable American migration into Texas occurred amid the following circumstances:
a. Ongoing Native American raids on Mexican villages.
b. A new Mexican nation in need of government revenue.
c. American westward expansion
d. All the Above

2. All the following contributed to the regional tensions which ultimately prompted seven southern states to declare their independence from the United States, EXCEPT:
a. Lincoln’s campaign platform and inaugural address promising to abolish slavery
b. Disputes over tariffs and Lincoln’s campaign platform and inaugural address promise to impose another tariff
c. Expanding federal authority even as the rural South felt it had limited authority and sway in federal elections and national politics.
d. The legal struggle over the status of the enslaved convinced many northern abolitionists that abolition would only come by empowering the enslaved to rise up and liberate themselves

As historical evidence suggests, the first move toward incorporation of new territories came in the form of American inviduals moving in as settlers. Then settlements grew, together with aspirations and demands. Westward expansion was a long and sustained effort in 19th-century America.

Regarding the second question, the tariff issue in Lincoln´s address was not an issue leading to the Civil War.