Which of your two selections do you consider most impactful on Westward Expansion during 1800-1848?

For the initial post, pick two (2) of the following historical events:
The Lewis and Clark Expedition
The Missouri Compromise
Independence of Texas
Mexican War of 1846-1848
The California Gold Rush

Then, address the following for your selections:
Which of your two selections do you consider most impactful on Westward Expansion during 1800-1848? Explain why.

Analyze the effects of the ideology of Manifest Destiny on the two historical events that you chose from the list.