Interesting subject and it is not off topic. The Mexican War has been by historians named a cause of the Civil War. My take on the information...

here's a bit missing from the overall final settlement with Mexico. The two treaties combined came to $25 million dollars plus the United States paid off Mexico's debts. Not a bad deal for land that was (except for the
lands north of the Monterey Bay california in California) considered a vast waste land. Americans had to build hundreds of miles of canels and aquaducts and enormous dam projects that took fifty years to even begin building to exploit any of wealth of the farms that would grow at the turn of the twentieth century. Mexico could have never funded dam projects like the Hoover Dam or those along the Sierra Nevadas. It was the American people and their taxes that made this vast desert into something liveable.
The Civil War advanced this progress by the vast populations escaping the War and its after effects and the mining that was needed to support the War.

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David Upton