Manifest Destiny

Manifest Destiny and the

U.S. Mexican War

In 1845, John O’Sullivan, a newspaper reporter, wrote that is was the nation’s “manifest destiny to overspread and possess the whole of the continent which Providence has given us for the development of the great experiment of liberty, and. . . self-government.”  O’Sullivan was giving name to the idea that Americans had long held.  Americans believed that they should grow the nation until it expanded from the Atlantic Ocean to the Pacific Ocean, overspreading the entire continent.  However, these lands were not completely unoccupied.  Indian tribes and Mexico controlled vast regions of the west, and the Oregon Territory partly explored by Lewis and Clark was co-owned by America and England.  Still, Americans view these lands as unoccupied, and longed to possess them. 

            In 1844, James K. Polk was elected the eleventh president of the United States.  Polk had campaigned on the promise of expanding the nation.  Polk vowed to annex Texas, which had won its independence from Mexico, and wrestle the Oregon Territory from England.  Americans agreed with Polk’s expansionist ideas.

            In 1846, England agreed to divide Oregon in half with America getting the southern half.  Now U.S. territory extended all the way to the shores of the Pacific Ocean in the north.  But Mexico still controlled the southwest.

            Polk was happy to get half of Oregon without having to fight England.  Trouble was brewing with Mexico over Texas.  Texas had won its revolution with Mexico in 1836.  But Mexico still longed to take it back.  Though Texas immediately applied to become a state in the United States, northern politicians blocked Texas’ admission to the Union for ten years.  Northern politicians feared that if they annexed Texas, Mexico would declare war on the United States.  The politicians of the north also feared that if Texas was allowed to join the Union, they would enter as a slave state, upsetting the balance of power in the senate.  Northern politicians did not want the slave states to gain power, so they fought against statehood for Texas vigorously!

            However, in 1845, President Polk convinced Congress to admit Texas as the 28th state.  The annexation of Texas angered Mexico; but there was another problem as well.  The United States believed the border with Mexico was the Rio Grande River.  Mexico thought the border with the United States was the Nueces River, one hundred miles further into Texas.  The land between these rivers was called the Disputed Territory.  Both countries claimed it, and this was bound to cause trouble.  

            Polk wanted more of Mexican lands than just the disputed Territory.  Polk wanted all of Mexico’s northern territories all the way to California on the Pacific Ocean’s coast.  America first tried to purchase the lands, much like they had purchased the Louisiana Purchase from France.  Polk sent John Slidell to Mexico City to offer $25 million for Mexico’s northern territories.  Besides, other than a few farms and missions, the settlement of Santa Fe in New Mexico, and a string of cities, farms, and towns in California, Mexico was hardly using these lands.  But Mexico refused to sell.  Mexico had only won its independence from Spain in 1821.  Since then, they had already lost Texas to the United States.  Now, the United States was asking to buy roughly one-half of their land!  This was simply unacceptable to Mexico. 


Mexico’s refusal was unacceptable to President Polk as well.  If the lands could not be bought, they would be taken in a war.  To this end, Polk sent General Zachary Taylor into the Disputed Territory.  Taylor placed his troops on the northern bank of the Rio Grande River.  In response, Mexico moved part of its army to the southern bank of the river.  Within days, Mexican cavalry units attacked American troops foraging for food.  American now had an excuse for war with Mexico. 

            When news arrived in Washington, D.C., President Polk asked Congress to declare war with Mexico.  Many northern politicians disagreed.  Illinois Representative Abraham Lincoln asked President Polk to show Congress exactly where on the map American blood had been shed, knowing it was in territory that was disputed between the two countries.  Northern politicians did not want America to go to war with Mexico, since any new lands gained there would be south of the Missouri Compromise Line of 1820, those lands could become slave states.  This would further upset the balance of power in the Senate between slave and free states.  However, western and southern congressmen outvoted the northern politicians.  War was declared.

            General Zachary Taylor moved south into Mexico, capturing the city of Monterrey and defeating Santa Anna’s army at the Battle of Buena Vista.  Santa Anna was both General of the Mexican Army, and the president of Mexico.  Santa Anna was forced to retreat from the Battle of Buena Vista partly as he took many looses in combat, but more importantly, his government in Mexico City was about to replace him as president.  To secure his government, he retreated and used his army to stay in power.

            In the north, General Kearny marched his army from Fort Leavenworth, Kansas to Santa Fe, New Mexico, a journey of 650 miles.  After taking New Mexico, he marched his army hundreds of miles more to California, seizing most of Mexico’s northern territory.

            In California, John C. Freemont was at work.  Freemont was a former American military officer who dreamed of stealing California for the United States.  At night, he and a band of American expatriates broke into the Mexican governor of California’s house and forced him to sign over the state of California and declare its independence from Mexico.    Stealing a bed sheet off of the Mexican governor’s bed, the group drew a crude picture of a grizzly bear with blackberry juice, and declared it to be the flag of the new, and independent Republic of California.  Known as the Bear Flag Revolt, this attempt to wrestle California from Mexico would have been short lived had not the armies of General Kearny arrived from Santa Fe, and Commodore Sloat’s forces not landed on the California coast to defeat the Mexican forces in California. 

            With General Kearny’s and Commodore Sloat’s forces in control of Mexico’s northern territories north of the Rio Grande River, all that remained was to finish the Mexican army to keep the acquired lands.  As General Zachary Taylor moved south, General Winfield Scott landed his forces at Vera Cruz on the Gulf of Mexico.  This was America’s first true amphibious assault. 

            General Scott’s forces took the walled city of Vera Cruz using artillery to bombard the city into submission.   Along the way to Mexico City, Santa Anna’s forces tried in vain to stop them.  Time and time again, Scott’s forces were able to defeat or outmaneuver the Mexican Army.  In the end, only the castle of Chapultepec stood in the Americans way.  Chapultepec was a citadel atop a mountain.  To reach the castle, American troops had to scale the cliffs and castle walls under heavy fire.  But, the defense of Chapultepec was a lost cause.  The 1,100 defenders, 100 of whom were teenage military cadets, were defeated.  The last defender of the castle, rumor holds, was a thirteen year old military cadet.  Once all was lost, rather than allow himself to be taken prisoner, the boy wrapped himself in the Mexican Flag that had flown over the castle, and jumped to his death on the rocks below.  With the fall of Chapultepec, Mexico City lay open to the American Army.  To allow himself time to escape; General Santa Anna released the prisoners in Mexico City to flood the streets with violence and slow the progression of the U.S. Army. 

            Mexico had been defeated.  Days later, the remains of the Mexican government signed the Treaty of Guadalupe-Hidalgo that ended the war.  In the Treaty of Guadalupe-Hidalgo, Mexico gave up their claims to the territories north of the Rio Grande River, called the Mexican Cession.  The Mexican Cession includes the present day states of California, Arizona, New Mexico, and parts of Texas, Utah, Colorado, and Wyoming.  This land area represented almost one-half of all of Mexico.  America also agreed to pay Mexico $15 million for the land, and pay off Mexico’s $3.25 million in debt it owed to citizens of the Untied States.  Finally, America agreed that the almost 80,000 Mexican citizens living in what was now American territories would be able to keep their lands, and be protected under U.S. laws. 

            Just five years later, in 1853, America once again decided it needed more of Mexico.  America wanted to build a transcontinental railroad to link the lands of the east and west coasts.  The Rocky Mountains made building a railroad through the territories American already possessed almost impossible.  However, there was a little slice of Mexico, just south of the new U.S. border where the mountains were widely spaced as they ran though the desert.  So, in 1853, America bought the Gadsden Purchase for $10 million dollars to build its transcontinental railroad. 

            Now, finally, America stretched from the Atlantic Ocean to the Pacific Ocean.  America’s dreams of Manifest Destiny had been achieved. 


The 49’ers


            A year after California was taken from Mexico in the U.S.-Mexican war, gold was discovered in California.  A carpenter working on a saw mill called Sutter’s Mill saw something sparkling in the water, reached in and pulled out a lump of gold.  When news of this discovery spread, thousands of people flocked to California to get rich quick, searching for gold. 

            In less than five years, more than 250,000 people had moved to California.  Some went west seeking the gold, but many more went west to make their living selling things to the miners.  This huge migration of people caused economic growth that changed California permanently.  The small port city of San Francisco grew quickly to become California’s center for manufacturing, trade, banking, and shipping. 

            This growth in California had negative effects as well.  Many Native Americans living in California were hunted down or pushed off native lands in the search for gold and farmland.  Many more died of disease brought by settlers and gold seekers.  Californios, people of Mexican or Spanish descent living in California lost most, or all, of their lands as well. Chinese immigrants that came to California to work the gold fields were discriminated against as well.  These groups were seen to be in the way of progress, and lost much in progress’s name.

            The most lasting result of the population explosion in California due to the gold rush was California’s admission to statehood in 1850.  California grew so fast it was allowed to skip the territorial stage, and apply for state hood immediately.  However, California’s admission to statehood caused problems on a national level.  California would enter the union as a free state.  This once again upset the balance of power in the Senate, causing the need for yet another compromise between pro and anti-slavery opponents.