Why did Americans want to expand westward, and why were they willing to go to war to secure the West?

Explanation: The Americans wanted to expand westward because they realized that large amounts of gold lay in this territory, especially in Coloma, in a sawmill called Sutter's Mill. Eager for a change to better life chances, many emigrations were made to that place. The number of emigrants to California was so great that this phenomenon was called The Gold Rush.

The Americans were willing to go to war to secure the West because many of them had settled in Texas, which was part of Mexico, thus beginning the United States-Mexico War, between 1846 and 1848 where it was intended to do expansion by the Americans adopting the doctrine of Manifest Destiny.

Manifest destiny. They believed it was their god given right to expand westward.