Manifest destiny was the idea that the United States would stretch from sea to sea as a beacon of liberty. Texas had lots of American immigrants at the time and had a lot of slave plantations that could of extended the south. Texas also had recently broken free from Mexico, and was made by American settlers who made their government based on the US. So, because of all this, America decided to annex Texas and incorporate it into the Union.
The Confederates retreated to Texas and never again threatened Union control of the Southwest..
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The people will stop thinking everything the church says is true.