Pros Of Annexation
From the Texans point of veiw
The main two reasons that Texas wanted annexation is because of Debt, and Protection.
If Texas did move into the United States, then they could borrow money from them because in this time Texas was 1000 dollars in debt so they could borrow money then when they earned enough money they could pay the United States back.
The 2nd reason they wanted to move into the United States was because they needed more protection. Mexico always wanted to get in a war with Texas. so if they moved to the United States they could get more protection
why the U.S did not want Texas
The U.S did not support Texas annexation because, at that time the U.S was trying to get rid of slavery and was on the very edge of the civil war. So of course they would not want another state with slavery especially one as big as Texas.