The Forgotten War That Created the American Southwest
1h 5m | Oct 9, 2026What did the Mexican-American War have to do with the Civil War, Manifest Destiny, Texas, California, and the modern American Southwest?
Jon Harris sits down with Thomas Wayne Riley of the American Southwest Podcast for a wide-ranging conversation about the Mexican-American War and the history that shaped the American Southwest.
The discussion begins with the enormous territorial consequences of the war and the idea of Manifest Destiny, before examining the border dispute that sparked the conflict and the American campaign into Mexico. They discuss the Mexican frontier, Texas independence, California, Mormon settlement, the growth of American communities in the Southwest, and the many future Civil War generals who gained military experience during the Mexican-American War.
The conversation also explores the war's connection to American expansion and imperialism, the San Patricio Battalion, the changing population of the Southwest, and the much older history of the region.
This is a conversation about the history between the American Revolution and the Civil War that is often overlooked, and why understanding that history helps explain the United States and the Southwest today.
00:00 – Introduction: The Mexican-American War and Modern America
06:00 – The Forgotten America Between the Revolution and Civil War
07:14 – Manifest Destiny and America's Expansion West
13:26 – How the Mexican-American War Began
20:35 – Life on the Mexican Frontier
24:21 – Population, Settlement, and the Growth of the Southwest
28:00 – Texas, California, and Mormon Settlement
35:00 – The Mexican War: Training Ground for Civil War Generals
42:02 – America's First Foray Into Imperialism?
52:58 – The San Patricio Battalion, Borders, and the Modern Southwest
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