The Mexican Cession was the land Mexico ceded (gave up)to the United States in the Mexican War. The cession covered what are now California, Nevada, Utah, and parts of four other states. World Book map

Mexican War (1846-1848) was fought between the United States and Mexico over disagreements that had been accumulating for two decades. In the course of the war, United States forces invaded Mexico and occupied the capital, Mexico City. By the Treaty of Guadalupe Hidalgo, the United States acquired from Mexico the regions of California, Nevada, and Utah, most of Arizona and New Mexico, and parts of Colorado and Wyoming. But many historians believe the war was an unnecessary attack on a weaker nation.

Causes of the war

Background of the war. In 1835, Texas revolted against the Mexican government, which then controlled the region. Texans established the Republic of Texas in 1836, but Mexico refused to recognize Texas' independence. The Mexican government warned the United States that if Texas were admitted to the Union, Mexico would break off diplomatic relations with the United States. James K. Polk was elected U.S. President in 1844. He favored the expansion of U.S. territory and supported the annexation of Texas. Texas was made a state in 1845, and Mexico broke off relations with the United States. At this point, the dispute could have been settled by peaceful means. But the United States wanted additional Mexican territory, and other quarrels developed.

One of these disputes was the question of the boundary between Texas and Mexico. Texas claimed the Rio Grande as its southwestern border. Mexico said that Texas had never extended farther than the Nueces River. Also, the U.S. government claimed that Mexico owed U.S. citizens about $3 million to make up for lives and property that had been lost in Mexico since Mexico's war for independence from Spain ended in 1821. By the 1840's, many Americans demanded that the United States collect these debts by force.

More important was a growing feeling in the United States that the country had a "manifest destiny" to expand westward into new lands (see MANIFEST DESTINY). The westward movement had brought Americans into Mexican territory, especially California. Mexico was too weak to control or populate its northern territories. Both American and Mexican inhabitants were discontented with Mexican rule. California seemed almost ready to declare itself independent.

Events leading up to the war. In the fall of 1845, President Polk sent John Slidell to Mexico as American minister. Slidell was to offer Mexico $25 million and cancel all claims for damages if Mexico would accept the Rio Grande boundary and sell New Mexico and California to the United States. If Mexico refused to sell the territories, Slidell was to offer to cancel the claims on condition that Mexico agreed to the Rio Grande boundary. While Slidell was in Mexico, a new Mexican president came to power. Both the old and new presidents were afraid their enemies would denounce them as cowards if they made concessions to the United States. They refused to see Slidell, who came home and told Polk that Mexico needed to be "chastised."

Meanwhile, Polk had ordered Major General Zachary Taylor, who was stationed with about 4,000 men on the Nueces River, to advance to the Rio Grande. Taylor reached the river in April 1846. On April 25, a party of Mexican soldiers surprised and defeated a small group of American cavalry just north of the Rio Grande.

Polk had wanted to ask Congress to declare war on Mexico. The news of the battle gave him the chance to say that Mexico had "invaded our territory and shed American blood on American soil." In reality, Mexico had as good a claim as the United States to the soil where the blood was shed. But on May 13, 1846, Congress declared war on Mexico.

The occupation of New Mexico and California. In June 1846, General Stephen W. Kearny set out with about 1,700 troops from Fort Leavenworth, Kans., to capture New Mexico. In August, the expedition entered the New Mexican town of Santa Fe and took control of New Mexico. The next month, Kearny pushed across the desert to California.

Meanwhile, in June 1846, a group of American settlers led by U.S. Army officer John C. Fremont revolted in California against the Mexican government. This rebellion became known as the Bear Flag Revolt because of the portrayal of a grizzly bear on the settlers' flag. In July, U.S. naval forces under Commodore John D. Sloat captured the California town of Monterey and occupied the San Francisco area. On December 6, Kearny led about 100 troops in the bloody Battle of San Pasqual near San Diego. Reinforcements from San Diego helped save the small American army. In January 1847, U.S. troops under Kearny and Commodore Robert F. Stockton of the Navy won the Battle of San Gabriel near Los Angeles. This victory completed the American conquest of California.

Taylor's campaign. Before war officially began, General Zachary Taylor had driven the Mexicans across the lower Rio Grande to Matamoros in the two battles of Palo Alto and Resaca de la Palma. These battles occurred on May 8 and 9, 1846. On May 18, Taylor crossed the river and occupied Matamoros. After waiting for new troops, he moved his army up the river and marched against the important city of Monterrey. Monterrey fell on September 24, after a hard-fought battle. Before the end of the year, Taylor had occupied Saltillo and Victoria, important towns of northeastern Mexico. However, Mexico still refused to negotiate with the United States.

Polk and his advisers decided to land an army at Veracruz, on the east coast, and strike a blow at Mexico City. Many of Taylor's best troops were ordered to join Major General Winfield Scott, who was placed in charge of the new campaign. President Antonio Lopez de Santa Anna of Mexico commanded the Mexican Army. He learned of the American plans and immediately led a large army against Taylor at Buena Vista, in the mountains beyond Saltillo. Although the Mexican forces nearly overran the U.S. positions, Taylor's troops eventually defeated them. General Taylor became a hero because of his victories and was elected President of the United States in 1848.

Doniphan's victories. In December 1846, Colonel Alexander W. Doniphan led about 850 troops south from Santa Fe to capture the Mexican city of Chihuahua. The American troops defeated a Mexican army at El Brazito on Christmas Day. Doniphan's army won the furious Battle of the Sacramento, fought just outside Chihuahua on Feb. 28, 1847. The Americans occupied the city on March 1.

Scott's campaign. General Scott was at this time the officer of highest rank in the United States Army. With a force of about 10,000 men, he landed near Veracruz on March 9, 1847. Twenty days later he captured the city, and on April 8 he began his advance toward the Mexican capital. The American army stormed a mountain pass at Cerro Gordo on April 17 and 18 and pushed on. Near Mexico City, American troops fought and won the battles of Contreras and Churubusco on August 19 and 20. The Mexican Army was superior in numbers but poorly equipped and poorly led.

After a two weeks' armistice, the Americans won a battle at Molino del Rey and stormed and captured the hilltop fortress of Chapultepec. On the following day the Americans marched into Mexico City.

The peace treaty. Despite all the American victories, Mexico refused to negotiate a peace treaty. In April 1847, Polk had sent Nicholas P. Trist, Chief Clerk of the Department of State, to join Scott's army in Mexico and attempt to open diplomatic negotiations with Santa Anna. When the armistice of August failed, the President recalled Trist. But Santa Anna resigned shortly after Scott entered the Mexican capital. Mexico established a new government, and it feared that it might lose even more territory if it did not accept the American demands. At the request of the Mexican leaders and General Scott, Trist agreed to remain in Mexico against Polk's orders and negotiate a settlement.

The treaty was signed on Feb. 2, 1848, at the village of Guadalupe Hidalgo, near Mexico City. By this time, many people in the United States wanted to annex all Mexico. But the treaty required Mexico to give up only the territory Polk had originally asked for. The United States paid Mexico $15 million for this territory, known as the Mexican Cession. In 1853, the Gadsden Purchase gave an additional 29,640 square miles (76,767 square kilometers) to the United States (see GADSDEN PURCHASE).

Results of the war. The United States gained more than 525,000 square miles (1,360,000 square kilometers) of territory as a result of the Mexican War. But the war also revived the quarrels over slavery. Here was new territory. Was it to be slave or free? The Compromise of 1850 made California a free state and established the principle of "popular sovereignty." That meant letting the people of a territory decide whether it would be slave or free. However, popular sovereignty later led to bitter disagreement and became one of the underlying causes of the American Civil War. See COMPROMISE OF 1850; POPULAR SOVEREIGNTY.

The Mexican War gave training to many officers who later fought in the Civil War. Civil War officers who also fought in the Mexican War included Ulysses S. Grant, William T. Sherman, George B. McClellan, George Gordon Meade, Robert E. Lee, Stonewall Jackson, and Jefferson Davis.

Palo Alto, pronounced PAL oh AL toh, was one of the earliest battles of the war. General Taylor's troops defeated Mexican forces under General Mariano Arista on May 8, 1846, on a plain northeast of Brownsville, Tex.

Resaca de la Palma, pronounced ray SAH kuh day lah PAHL muh. A 2,300-man army under Taylor crushed 5,000 Mexican soldiers under Arista in Cameron County, near Brownsville, Tex., on May 9, 1846. General Taylor's two victories allowed him to cross the Rio Grande and to invade Mexico.

Buena Vista, pronounced BWAY nah VEES tah. Near the ranch of Buena Vista, Mexico, Taylor's force of about 5,000 men defended a narrow mountain pass against Santa Anna's army made up of from 16,000 to 20,000 men. Through this battle, fought on Feb. 22 and 23, 1847, the American forces established their hold on northeastern Mexico.

Cerro Gordo, pronounced SEHR oh GAWR doh, ranks among the most important battles the Americans fought on the march from Veracruz to Mexico City. A mountain pass near Jalapa, Cerro Gordo lies 60 miles (97 kilometers) northwest of Veracruz. General Scott's 9,000-man force attacked 13,000 Mexicans under Santa Anna, and forced them to flee. The battle, fought on April 17 and 18, 1847, cleared the way to Mexico City.

Churubusco, pronounced choo roo VOOS koh. In the small village of Churubusco, 6 miles (10 kilometers) south of Mexico City, Scott's invading army won another major victory on Aug. 20, 1847. Scott's soldiers stormed the fortified camp of Contreras, then attacked the Mexican force at Churubusco. The Mexicans finally fled, and sought refuge within the walls of the capital city. The Americans had about 9,000 men in the battle; the Mexicans, about 30,000.

Chapultepec, pronounced chuh PUHL tuh pehk, was the last battle of the war before the capture of Mexico City. On Sept. 12, 1847, Scott's men attacked Chapultepec, a fortified hill guarding the city gates. The attacks continued the following day until the Mexicans retreated to Mexico City. On September 14, Scott's troops entered the Mexican capital.

Contributor: Joseph A. Stout, Jr., Ph.D., Prof. of History, Oklahoma State Univ.

Additional resources

Eisenhower, John S. D. So Far from God: The U.S. War with Mexico. Random Hse., 1989.

McCaffrey, James M. Army of Manifest Destiny: The American Soldier in the Mexican War. New York Univ. Pr., 1992.

Nardo, Don. The Mexican-American War. Lucent Bks., 1991. Younger readers.

Robinson, Cecil, ed. The View from Chapultepec: Mexican Writers on the Mexican-American War. Univ. of Arizona Pr., 1989.