Not everyone was as enthused over the idea of
Manifest Destiny as were the Americans. Still seething over the loss of
Texas, Mexican authorities were concerned over the possibility of
giving up the vast region west of Texas, including California, to the
United States. These and other factors led to a war between the United
States and Mexico, finally breaking out in 1846.
|The influence of Spanish
culture was evident throughout California and the southwest. A Spanish
mission is shown above. Image courtesy of Library of Congress.
Mexico's claim on California and the southwest
was inherited from the
Spaniards, dating back to the 15th century. Spanish law, architecture,
culture, and language prevailed throughout the area. However, Mexico's
grip on the territory was weak at best, in large part due to sparsely
populated regions, poor administration and a revolving door of corrupt
In 1845, tensions between the United States and Mexico mounted as the
dispute over the southern boundary of Texas magnified. The Mexican
government asserted the boundary between Texas and Mexico was the
Nueces River, while the Americans maintained that it was the Rio Grande
River, about a hundred miles to the south of the Nueces, that separated
the two nations.
|James K. Polk is rated as one
of the most effective presidents in US history, who met the demands of
office with perseverance and great administrative skill. Under his
watch, the US expanded all the way to the Pacific Ocean. The only
president ever to achieve all of his platform goals, Polk declined to
run for a second term. Three months after leaving the White House, the
Tennessean was dead. Image courtesy of the National Archives.
When it appeared the Mexicans were willing to
negotiate the dispute
peacefully, President Polk secretly dispatched congressman John Slidell
to Mexico City in November 1845, with instructions to pay off claims of
about $2 million by American citizens against Mexico, if Mexico would
acknowledge the Rio Grande as the southern boundary of Texas.
Furthermore, Polk authorized an offer of $25 million for the purchase
of California and $5 million for the New Mexico territory.
When news of Slidell's mission was leaked, the Mexican populace was
incensed over what they perceived as yet another American expansionist
scheme at the expense of Mexico.
Meanwhile, the Mexican government refused to speak with the American
envoy, sending him home empty-handed. Mexican newspapers ridiculed
American diplomacy and military prowess and called for a "necessary"
war against the United States. Mexican army leaders bragged they could
defeat their northern neighbor in a military confrontation, based on
their experience at expelling the Spaniards and putting down internal
revolutionists. They also assumed Great Britain would come to their
aid, because the British had opposed the United States' annexation of
Texas. They also believed American public opinion would be sharply
divided over support of a war. Clearly, Mexico was itching for a fight.
|News of the Mexican War hits
the home front, as shown in this engraving based on the 1848 painting
by R.C. Woodville. Image courtesy of Humanities-Interactive.
In January 1846, President Polk ordered troops
under General Zachary
Taylor to cross the Nueces River, southward into the disputed zone, to
the northern bank of the Rio Grande. In May, Mexican troops crossed the
Rio Grande and skirmished with American forces, killing or wounding
sixteen. If Polk had been waiting for an excuse to ask Congress for a
declaration of war against Mexico, he now had it. On May 13, Congress
obliged. War with Mexico was on.
It soon became apparent that Mexico's boast of military superiority was
premature. Even though the Mexican army was four times the size of the
American army, the natural resources and industrial might of the United
States enabled its troops to be better equipped and supplied. Many
reservists were quickly called into active duty to rectify the initial
imbalance of manpower. They were all trained and led by competent
graduates of the national military academy at West Point. In addition,
the small, but well organized American navy was capable of ferrying
troops to within 250 miles of Mexico City. With these advantages,
American military strategists were able to devise a war plan consisting
of three fronts that effectively subdued the Mexicans.
The first front was to commence from the Rio Grande, where General
Taylor's army sat primed to go. Taylor became a national hero following
his victory at Buena Vista, giving control of northern Mexico to the
Americans. Another group of Americans, led by General Stephen Kearny,
marched from Fort Leavenworth, Kansas, to Santa Fe, taking possession
of the New Mexico territory. From there, Kearny proceeded to California
and joined with Captain John C. Frémont (who had established
temporarily the Republic of California, a.k.a. the Bear Flag Republic)
and other American forces, to completely overcome Mexican resistance in
|General Winfield Scott
(center, on brown horse facing right) parades the US army in Mexico
City's main square. To the right of the cathedral is the National
Palace, built atop the ruins of the Halls of Montezuma. Image
courtesy of University of Texas at Arlington Libraries.
A third expedition, under the command of General
Winfield Scott, hit
Vera Cruz following an amphibious landing in March 1847 of 14,000 men
from the Gulf of Mexico.
From there, the Americans embarked on a tortuous journey toward Mexico
City, following the route traveled by Hernando Cortez centuries
earlier. Nearly every step of the uphill, mountainous road leading to
the "Halls of Montezuma" was bitterly challenged. Several difficult
battles were fought along the way, but Scott continued to advance.
After the fall of Chapultepec, the last major line of Mexican defense,
American troops entered Mexico City as conquerors on September 14,
1847. For all practical purposes, the Mexican War had come to an end.
|The map of the United States
in 1848, following Mexican War. The pink to the left is the region
ceded by Mexico. The blue in the upper left is the Oregon Country. The
middle green is the state of Texas, while large yellow area is
remainder of Louisiana Purchase yet to be organized into states. Image
courtesy of Humanities-Interactive.
The Treaty of Guadalupe Hidalgo, signed on
February 2, 1848, formally
ended the war. Mexico was forced to give up California, the New Mexico
territory, and recognize the Rio Grande as the border between Texas and
In return, the United States paid Mexico $15 million and agreed to
assume debts totaling over $3 million that Mexico owed to American
citizens. From the "Mexican Cession" ultimately shaped the states of
California, Nevada, and Utah, and parts of Arizona, New Mexico,
Colorado, and Wyoming.
In 1853, Congress approved a payment of $10 million to Mexico for the
purchase of some 50,000 square miles of desolation along the southern
tip of what is today Arizona and New Mexico. The Gadsden Purchase, as
it was called, was thought to be suitable for a southern
transcontinental railroad being contemplated. Except for Alaska, the
Gadsden Purchase filled out the present continental boundaries of the
The dreams of all Americans who had believed in their nation's Manifest
Destiny had materialized. The boundaries of the United States now
reached from sea to shining sea.