Texas Annexation — Texas Joins the Union as the 28th State


The Texas Annexation was a series of events that led to Texas joining the United States as the 28th state in the Union on December 29, 1845. The annexation of Texas was a direct cause of the Mexican-American War and contributed to the growing section divide over slavery that led to the Civil War in 1861. However, annexation expanded the economy and increased safety for Americans living on the western frontier.

President John Tyler, Portrait

President John Tyler. Image Source: Wikipedia.

Texas Annexation Summary

The Texas Annexation — also known as the Annexation of Texas — refers to the series of events that led Texas to become the 28th state in the Union. Following the Texas Revolution (1835–1836), Mexico refused to recognize the treaties that ended the conflict. As a result, Texas sought the protection of the United States and voted to join the Union.

However, the threat of war with Mexico and anti-slavery sentiment made annexation impossible until the end of the administration of President John Tyler. In 1843, Tyler negotiated a treaty with Texas but it was rejected by Congress.

The Annexation of Texas became a key issue during the Election of 1844, which was won by “dark horse” Democratic candidate, James K. Polk. Tyler, determined to bring Texas into the Union, was able to push a joint resolution through Congress that approved the statehood of Texas.

Despite protests and schemes from Mexico, Great Britain, and anti-slavery factions in the United States, Texas voted to accept annexation to the United States on July 4, 1765. Texas was formally admitted to the Union on December 29, 1845, which laid the foundation for the Mexican-American War, which started in May 846.

Texas Annexation Dates and Facts

  1. Texas declared independence from Mexico on March 2, 1836, and established the Republic of Texas.
  2. Texas won the Battle of San Jacinto on April 21, 1836, ending the Texas War for Independence.
  3. U.S. President John Tyler agreed to a treaty to annex Texas in 1843, but the Senate rejected the treaty on June 8, 1844.
  4. Democrat James K. Polk won the Election of 1844, running on an expansionist platform that included an intent to “re-annex” Texas.
  5. Outgoing President Tyler had the treaty introduced to Congress as a joint resolution.
  6. The final version of the resolution was approved by the Senate on February 27, 1845, and the House of Representatives on February 28, 1845.
  7. President Tyler signed the legislation on March 1, 1845.
  8. James K. Polk was sworn in as President on March 4, 1845.
  9. The Congress of Texas approved the annexation on June 23, 1845, and a special Annexation Convention approved it on July 4, 1865.
  10. Texas voters approved a new state constitution and annexation on October 13, 1865.
  11. The U.S. Congress approved the new Texas constitution on December 29, 1845, making Texas the 28th state in the Union.
  12. On February 19, 1846, James Pinckney Henderson was sworn in as Governor of Texas.
Mexican American War, Nueces Strip, Illustration
This map shows the territory of Texas in 1846, however, Mexico also claimed a significant amount of the territory. Image Source: U.S. Army Center of Military History.

Texas Annexation History and Overview

During the Texas Revolution (1836–1836), Mexico believed the United States encouraged the uprising to annex Texas. Following the Battle of San Jacinto (April 21, 1836), General Antonio López de Santa Anna agreed to the Treaties of Velasco with the people of Texas. 

The treaties identified the Rio Grande River as the southern border of Texas and recognized Texas as an independent state. At the time, Texas included parts of present-day New Mexico, Colorado, and Arkansas. From the end of the Texas Revolution until the start of the Mexican-American War, the controversy over the Republic of Texas was a complex issue that involved the United States, Mexico, and Great Britain.

Andrew Jackson Rejects Annexation of Texas

The first issue arose when the Mexican Government refused to approve the treaties or recognize the independent Republic of Texas, claiming Santa Anna had been coerced into agreeing. 

In September, the people of Texas, fearing Mexican aggression, sought the protection of the United States. They voted to join the United States and Texas officials tried to open negotiations with the administration of President Andrew Jackson. However, Jackson delayed negotiations for various reasons:

  1. 1836 was an election year and Jackson did not want the issue of annexation to affect the election
  2. Mexico told the United States that if it annexed Texas, it would be considered an Act of War.
  3. Slavery was legal in Texas and the addition of a pro-slavery territory would upset the balance between Free States and Slaves States in Congress.

On his last day in office, President Jackson signed legislation recognizing the Republic of Texas.

Andrew Jackson, Portrait, Painting
President Andrew Jackson. Image Source: Wikipedia.

Martin Van Buren Rejects Annexation of Texas

In November 1836, Martin Van Buren was elected the 8th President of the United States. He took office on March 4, 1837. A Texas official, Memucan Hunt Jr., presented Van Buren with the Texas proposal, but Van Buren rejected it in August. 

Constitutional issues and threats of war with Mexico were given as the main reasons for rejection. However, it is generally accepted that anti-slavery sentiment in the United States, particularly in the North, also played a role.

Resolutions for annexation were also introduced in the Senate and House of Representatives and were defeated.

President Lamar Opposes Annexation of Texas

Not everyone in Texas favored annexation. One of the most vocal opponents was President Mirabeau B. Lamar, who was elected President of Texas in 1838. 

At his inauguration address, he said, “I cannot regard the annexation of Texas to the American Union in any other light than as the grave of all her hopes of happiness and greatness; and if, contrary to the present aspect of affairs, the amalgamation shall hereafter take place, I shall feel that the blood of our martyred heroes had been shed in vain.” 

The offer to the United States for annexation was withdrawn on October 12, 1838.

Mirabeau B. Lamar, President of Texas
Mirabeau B. Lamar, President of Texas. Image Source: New York Public Library Digital Collections.

John Tyler Becomes President of the United States

Two years later, William Henry Harrison defeated Martin Van Buren in the U.S. Election of 1840. After he delivered his inaugural speech in cold, wet weather, Harrison developed pneumonia. He died at 12:30 a.m. on April 4, 1841, and was succeeded in office by Vice President John Tyler.

Following Tyler’s ascension to the Presidency, events started to take place that would lead to the eventual annexation of Texas.

  1. Sam Houston was elected President of Texas in 1841 and favored annexation. Unlike Lamar, Houston supported annexation but also wanted to ensure the terms favored Texas.
  2. In 1842, Texas extended its border West to the Pacific Ocean, which included portions of California and northern Mexico.
  3. By 1843, the United States was concerned about Great Britain’s interest in Texas. Great Britain did not want to annex Texas, but it did want to trade with Texas, as did other European nations. Tyler and other supporters of slavery were also concerned the British would try to emancipate slaves in Texas.
  4. 1844 was an election year. President Tyler believed the Annexation of Texas would aid him in his re-election effort.

The Senate Rejects the Tyler-Texas Treaty and Annexation

Tyler re-opened negotiations with Texas regarding annexation in October 1843, sending Secretary of State Abel P. Upshur of Virginia to meet with Isaac Van Zandt, the Texas minister to the United States. The United States and Texas agreed to a treaty, which would admit Texas into the Union as a territory. 

The “Tyler-Texas Treaty” was submitted to the Senate in April 1844. Secretary of State, John C. Calhoun, included a letter with the treaty, known as the “Packenham Letter,” that appealed to the pro-slavery faction. Despite Calhoun’s effort, the anti-slavery faction in Congress — Whigs and Northern Democrats — defeated the proposal on June 8, 1844, by a vote of 35 to 16.

Tyler looked for an alternative to gaining approval for adding Texas to the Union, however, the Annexation of Texas became a key issue for both Whigs and Democrats in the Election of 1844.

The Election of 1844

Henry Clay, the Whig candidate, did not fully endorse annexation. He was not opposed to it, but he was cautious and expressed concerns over the risks. Clay was concerned annexation would lead to war with Mexico and increase the sectional divide over slavery.

For the Democrats, the path to electing a nominee was complicated. Tyler dropped out of the race, and Martin Van Buren, who was considered the favorite, opposed annexation. A third candidate, James K. Polk from Tennessee, fully endorsed annexation, and promised to “re-annex Texas.” Polk, the “dark horse candidate,” won the nomination with support from Andrew Jackson — and then narrowly defeated Clay in the election.

James K Polk, 11th President, Portrait
President James K. Polk. Image Source: National Portrait Gallery.

Congress Approves Texas Annexation

When the members of Congress returned to Washington, D.C. in December, President Tyler resumed his effort to gain approval for the Tyler-Texas Treaty. He was especially concerned action needed to be quickly taken to subvert any British involvement in Texas.

Tyler proposed the treaty be introduced as a joint resolution, which would only require a majority vote in both the Senate and the House. However, there was one significant change. The resolution allowed Texas to enter the Union as a state instead of a territory, which increased the chances Texas would accept the offer. 

With Polk’s support, the joint resolution was passed. The House of Representatives passed the resolution on January 25, 1845. The Senate approved it — just barely — by a vote of 27-25 on February 27, 1845. The next day, the House adopted the Senate version of the joint resolution by a vote of 132 to 76.

Tyler signed the resolution on March 1, 1845 — three days before Polk was sworn in as President. On his last day in office, Tyler sent the annexation offer to the President of Texas, Anson Jones, informing him the state would be admitted to the Union as soon as it approved annexation.

Mexico and Great Britain Respond

Mexico responded to the passage of the joint resolution by recalling its minister to the United States, Juan Almonte, from Washington. Almonte requested his passport on March 6, effectively cutting off diplomatic relations between Mexico and the United States. However, the President of Mexico, José Joaquin Herrera, did not want to pursue war and looked for other ways to block annexation.

The British hoped to prevent annexation by convincing Texas to decline the offer. On British advice, the government of Mexico agreed to acknowledge the independence of Texas on the condition that it would agree not to annex itself to any country. On May 19, Texas and Mexico signed the “Cuevas-Smith Treaty,” and Texas agreed to the terms that had been proposed by Great Britain.

Texas Approves Annexation

Public opinion in Texas, influenced by special agents sent from the United States, supported acceptance of the American offer for annexation. 

Texas President Anson Jones called for the Texas Congress to meet on June 16, 1845, and for an Annexation Convention of elected delegates to meet on July 4. Anson presented both bodies with the options he had been given:

  1. The offer from Mexico to recognize the independent Republic of Texas.
  2. Annexation to the United States as a new state in the Union.

The Congress of Texas approved the annexation on June 23, 1845, and the Annexation Convention voted in favor on July 4. Afterward, the Congress of Texas drafted a new state constitution.

America’s Manifest Destiny

In the United States, the Annexation of Texas was supported by the Slave States of the South, as it would likely be admitted with slavery intact. However, the annexation was opposed by anti-slavery advocates in the North.

On July 1, newspaper editor John O’Sullivan coined the phrase “Manifest Destiny.” Arguing in favor of annexing Texas, O’Sullivan said, “Annex the Republic of Texas, not only because Texas desired this, but because it was our manifest destiny to overspread the continent allotted by Providence for the free development of our yearly multiplying millions.”

John O’Sullivan. Image Source: Wikipedia.

Polk Prepares for Invasion

After Texas approved annexation, President Polk started to make preparations for Mexico to invade Texas. He ordered the commander of the U.S. Army in Texas, Zachary Taylor, to move his forces into the disputed lands that lay between the Nueces and Rio Grande rivers. 

Texas Joins the Union as the 28th State

On December 16, the House of Representatives voted to annex Texas by joint resolution, by a vote of 141 to 58. 21 members abstained from the vote.

Six days later, on December 22, the Senate approved the Joint Resolution, voting 31 to 14 in favor. 7 Senators abstained from the vote.

President Polk signed the joint resolution on December 29, 1845, and Texas officially entered the Union. 

However, the formal transfer of power was done in a ceremony that took place on February 19, 1846. At the ceremony, Texas President Anson Jones declared “The final act in this great drama is now performed; the Republic of Texas is no more,” and James Pinckney Henderson assumed the office of Governor of Texas. The flag of the Republic of Texas was lowered and the United States flag was raised.

The United States Inherits the Dispute with Mexico Over the Border

With annexation complete, American officials hoped it would give them an opportunity to discuss the border with Mexico. However, annexation only heightened tension, especially over the “Nueces Strip” — the disputed territory between the Nueces River and the Rio Grande River. Mexico insisted the Nueces River was its northern border, while Texas believed it was roughly 100 miles further south, at the Rio Grande River.

Texas Annexation Outcome

For the United States, the annexation of Texas was a significant expansion of the nation’s territory and resources. However, it also increased tension with Mexico and the internal debate in the United States regarding slavery.

Texas Annexation — A Cause of the Mexican-American War

By the time Texas was admitted to the Union, American forces were already in the territory, preparing for hostilities.

In November, Polk dispatched Congressman John Slidell to Mexico with instructions to negotiate the purchase of the disputed areas along the Texas-Mexican border, and the territory comprising the present-day states of New Mexico and California.

When Slidell’s mission failed in May 1846, Polk used news of skirmishes inside disputed territory between Mexican troops and Taylor’s army to gain Congressional support for a declaration of war against Mexico. On May 13, 1846, the United States declared war on Mexico. 

Thornton Affair, 1836, Illustration
This illustration depicts the Thornton Affair. Image Source: Pictorial History of the Mexican War (1850), Archive.org.

Texas Annexation Significance

The Texas Annexation is important to United States history because it led to the addition of Texas as the 28th state in the Union, and set the stage for the outbreak of the Mexican-American War in 1846.

Texas Annexation was a key moment during the Presidency of James K. Polk, who was an advocate of “Manifest Destiny” — the idea that America had a “divine right” to spread across the continent, from coast-to-coast. However, Texas Annexation also contributed to the national divide over slavery, which was a primary cause of the Secession Crisis and the outbreak of the Civil War in 1861.

Annexation of Texas APUSH Study Guide

Use the following links and videos to study Texas Annexation for the APUSH Exam.

Texas Annexation APUSH Definition

The Texas Annexation refers to the process by which the Republic of Texas, an independent nation that had previously been a territory of Mexico, was annexed by the United States and admitted to the Union as the 28th state in 1845. The annexation was controversial and was a direct cause of the Mexican-American War, and a contributing cause of the Civil War.

Annexation of Texas APUSH Unit 5: 1844–1877

This video discusses the history of the Texas Annexation.

Citation Information

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  • Article Title Texas Annexation — Texas Joins the Union as the 28th State
  • Date 1844–1845
  • Author
  • Keywords Texas Annexation, Texas Revolution, Mexican-American War
  • Website Name American History Central
  • Access Date June 16, 2024
  • Publisher R.Squared Communications, LLC
  • Original Published Date
  • Date of Last Update June 2, 2024