Expansion Era
Manifest Destiny drove the United States westward through wars of conquest against Mexico and prolonged campaigns against Native American nations. These wars dramatically expanded US territory at enormous human cost.
$2.5B
Total Cost (2023 $)
13,283
US Deaths
25,000
Civilian Deaths
1
Conflicts
1
Authorized by Congress
0
No Authorization
$2.5B
Costliest: Mexican-American War
13,283
Deadliest: Mexican-American War
Cost by Conflict (Billions, 2023 $)
Deaths by Conflict
🗽 Libertarian Analysis
Manifest Destiny was empire-building dressed up in patriotic language. The Mexican-American War was a war of conquest based on a presidential lie — the exact scenario the Founders tried to prevent by giving Congress the war power. The territory seized reignited the slavery crisis, leading directly to the Civil War. Wars of expansion always have unintended consequences.
⚖️ Constitutional Authority
Polk manufactured the Mexican-American War by placing troops in disputed territory and lying to Congress. Lincoln, then a congressman, challenged this deception with his "Spot Resolutions." The precedent of presidential provocation leading to congressional rubber-stamping was established here.