How did the united states come to own the land on the west coast of north america

In 1819, the United States acquired the Spanish claims to the Pacific Northwest (as negotiated in the Nootka Convention) in the Adams-Onís Treaty. ... Americans continued arriving on the west coast of North America in significant numbers in the mid-1830s.

Explanation:

not to sure sdi, strategic defense initiative

a. because the u.s. was the leading with the most technology, economy, etc. also was teamed with other allies witch boosted the economy and materials to improve technology and use it.