What is the cause of the prosperity of a nation according to adam smith?

Adam Smith and "The Wealth Of Nations" ... On March 9, 1776, "An Inquiry into the Nature and Causes of the Wealth of Nations" (commonly referred to as simply "The Wealth of Nations") was first published. Smith, a Scottish philosopher by trade, wrote the book to upend the mercantilist system.

From mexican american war , us gained new mexico.