---
title: "Manifest Destiny Definition | Model Diplomat"
description: "Manifest Destiny was the 19th-century belief that the U.S. was destined to expand across North America, influencing American policy and identity."
url: "https://modeldiplomat.com/learn/glossary/manifest-destiny"
---

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Model Diplomat Research Team · Last reviewed June 22, 2026

TL;DR

- Manifest Destiny was the 19th-century American belief that the United States was divinely ordained to expand its territory and democratic institutions across the North American continent.
- Who coined the term 'Manifest Destiny' and when?
- How did Manifest Destiny relate to the Mexican–American War?
- Why did Manifest Destiny intensify sectional tensions?

[Civil Service & Diplomatic Exams](https://modeldiplomat.com/learn/civil-services/glossary)Updated June 22, 2026

Manifest Destiny was the 19th-century American belief that the United States was divinely ordained to expand its territory and democratic institutions across the North American continent.

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In 1845 the journalist John L. O'Sullivan wrote of America's "manifest destiny to overspread the continent," supplying the ideological justification President James K. Polk used to wage the Mexican–American War (1846–1848).

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