How Did Texas Become Part of the United States?

Brigid Rowlings, Alexandra Lutz
  • Author
    Brigid Rowlings

    Brigid Rowlings has taught middle and high school History, Social Studies, Humanities, English Language Arts, and Gifted and Talented Enrichment for over 20 years. She has a B.A. in History and Literature from Harvard University and an M.A. in Liberal Arts from St. John's College. She also has a CAGS in Gifted Education and Talent Development from the University of Connecticut. Brigid is certified to teach middle and high school English Language Arts, History/Social Studies, and ESL in the state of Massachusetts.

  • Instructor
    Alexandra Lutz

    Alexandra has taught students at every age level from pre-school through adult. She has a BSEd in English Education.

Learn about Texas Annexation in 1845, the reasons for it, and its impact on the United States. Read about the importance of Manifest Destiny to the annexation. Updated: 04/28/2022

Table of Contents


Texas Annexation in 1845: Overview

Texas won independence from Mexico in 1836 at the end of the Texas Revolution. The United States chose not to annex, or add Texas to its territory at that time. Annexing Texas would have caused a variety of problems at the time, including increasing tensions around slavery spreading into the West and the potential for war with Mexico. Texas existed as an independent republic until 1845, when the United States finally annexed it, admitting Texas to the Union as the 28th state.

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  • 0:05 The Republic of Texas
  • 1:20 The Texas Problem
  • 2:04 The Texas Debate
  • 3:10 The Texas Treaty Defeat
  • 3:43 Texas Finally Becomes a State
  • 4:34 Lesson Summary
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Why Was Texas Annexed?

Shortly after gaining independence, Texans voted to be annexed by the United States in 1836. Texans wanted the political and economic advantages that would come with being a part of the United States and the military protection that would help Texans protect themselves against Mexico and Native American peoples.

Initially, President Andrew Jackson and President Martin Van Buren rejected annexing Texas because slavery existed in Texas, and the issue of slavery in the West was threatening to tear the nation apart. Texas annexation finally occurred in 1845. President John Tyler annexed Texas because of its strategic position near the port of New Orleans and because the doctrine of Manifest Destiny was driving American expansion from sea to shining sea.

Manifest Destiny and Texas Annexation

Manifest Destiny was the belief that God had destined the United States to extend from the Atlantic Ocean to the Pacific Ocean. The idea that the United States should span the North American continent was not new. The idea led President Thomas Jefferson to purchase the Louisiana Territory from France before sending Lewis and Clark and their Corps of Discovery on their famous expedition. The term Manifest Destiny was new, however. The journalist John O'Sullivan first used this term in an 1845 article in which he advocated for the annexation of Texas.

American Progress in an 1872 painting by John Gast. The angel striding towards the West represents Manifest Destiny.

American Progress is an 1872 painting by John Gast. The angel striding towards the West represents Manifest Destiny.

The Expansion of Slavery and Texas Annexation

When Stephen Austin brought the first American settlers to Texas in 1821, those settlers brought slaves with them. Although Mexico outlawed the slave trade in 1823 and outlawed slavery outright in 1829, Mexico gave American settlers a grace period. They could keep their slaves until 1830.

However, the American settlers did not want to give up their slaves. The issue of slavery became one of the reasons Texans declared and fought for independence from Mexico. When Texas won its independence from Mexico, Texans kept their slaves. Unfortunately, because the issue of slavery in the West was causing tensions in Congress and threatening to tear the United States apart, Texas's petition to enter the Union as a slave state was delayed for almost ten years.

How Did Texas Become Part of the United States?

Texans requested annexation by the United States for the first time in 1836. Although President Andrew Jackson had tried to buy Texas from Mexico, when Texas won independence, Jackson said he would not annex Mexico without approval from Congress. Because of the differing viewpoints on the expansion of slavery into the West, Congress did not favor annexation. Jackson's successor, President Martin Van Buren, also rejected the request. Van Buren feared that annexing Texas would accelerate tensions in Congress and potentially move the United States towards a civil war. Van Buren also feared entering into a war with Mexico.

President John Tyler strongly favored annexing Texas. After he was elected president, Tyler sent envoys to Texas to negotiate an annexation treaty, which he introduced to Congress on April 22, 1844. The Tyler-Texas Treaty was hotly debated in Congress and ultimately defeated. However, on his last day as president, Tyler sent an offer of annexation to Texas by courier, which they accepted. Tyler's successor, President James K. Polk, could have rescinded the offer. However, because Polk had run on the platform of Manifest Destiny, he let the offer stand.

The Texas Revolution

France and Spain had once controlled Texas before it became a part of Mexico. In 1821, Stephen Austin entered an agreement with the Mexican government to bring a group of American settlers to Texas. Mexico initially agreed to this settlement because the territory was sparsely settled, and Mexico believed the Anglo settlers would help protect Mexico and Mexicans against attacks by native peoples.

At first, the Mexican government allowed the American settlers to bring their slaves and granted the American settlers tax breaks. But, as the decade went on, the Mexican government became more restrictive, first limiting the number of American settlers that could enter Texas and then making moves to outlaw slavery. Finally, Mexico rescinded the tax breaks it had promised American settlers. The settlers declared independence from Mexico on March 2, 1836. After a brief war known as the Texas Revolution, Mexico recognized Texas's independence in the Treaty of Velasco.

Debate in Congress Over Texas Annexation

The debate in Congress over the Tyler-Texas treaty was heated. Those against annexing Texas argued that it would spread slavery even further West and drive the United States closer to a civil war. Opponents also pointed out that Mexico did not want the United States to annex Texas and become its neighbor; they believed annexing Texas could lead to war with Mexico. Those who supported annexing Texas reminded the other Congress members of the United States Manifest Destiny. They also pointed out that Great Britain was working hard to prevent the annexation. Great Britain wanted to prevent the United States from expanding further westward and becoming more of a global political and economic superpower.

When Did Texas Join the United States?

Texas annexation became a reality on July 4, 1845, when the Texan Congress voted to approve the annexation treaty. President Polk finished the work that President Tyler had started when he signed legislation making Texas the 28th state on December 29, 1845.

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Frequently Asked Questions

Why did Mexico not want Texas to be annexed?

Mexico did not want Texas to be annexed because Mexico claimed Texas as its own. Also, Mexico did not want the powerful United States at its northern border.

Why was the annexation of Texas so controversial?

The annexation of Texas was controversial because the early settlers in Texas brought slaves. The issue of the expansion of slavery into the West was threatening to tear the nation apart. Also, the annexation was controversial because the United States feared it would lead to war with Mexico.

Why was annexing Texas denied in 1844?

President John Tyler's effort to ratify the Tyler-Texas Treaty in 1844 failed because Congress would not ratify it. Congress feared that ratifying the treaty would cause a war with Mexico and increase tensions in the United States over slavery in the West. Congress was afraid annexing Texas could start a civil war.

When was Texas officially annexed?

Texas applied for annexation in 1836 but was not officially annexed until 1845. Once it was annexed, Texas became the 28th state of the United States.

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