Sep 16, 1810
El Día de Independencia in Mexico is a current national holiday that commemorates this date—the start of the country's war for independence from Spanish imperial control. (The holiday actually begins on the evening of the 15th.)
Feb 22, 1819
The Adams-Onis Treaty with Spain is signed in Washington, allowing for the American purchase of Florida. In exchange, the U.S. gives up all claims to Texas. The subsequent outcry condemns Secretary of State (and future president) John Quincy Adams for allowing "the loss of Texas," and subsequently a scramble ensues to acquire Texas by purchase.
Jan 1, 1819
Mexico starts to populate Texas. But Mexican liberals and even Yorkinos (the radical populist faction in Mexico) of the federal republic wind up in charge of the colonization effort. These people greatly admire North American entrepreneurship and culture.
Sep 27, 1821
Mexico achieves full independence from Spain.
Nov 7, 1835
Texas forms a provisional government at San Felipe de Austin. Its council shows support for the 1824 Mexican Constitution and it appoints a governor, but does not yet declare independence.
Dec 20, 1835
In Goliad, local Tejanos and Anglo-Texan settlers sign the first declaration of independence for Texas.
Jan 1, 1836
Texas is under the control of the Mexican state of Coahuila, and the capital at Saltillo is so far to the south that many Texans find it annoyingly distant. A new Mexican Constitution, enacted in 1836, abolishes states entirely, antagonizing Texans further by requiring all administration to be based in far-off Mexico City.
Feb 23, 1836
5,000 Mexican soldiers under General Santa Anna lay siege to the Alamo, a mission church in San Antonio, Texas, being used as a makeshift fortress by Anglo-Texan rebels. 13 days later, on March 6th, the Mexican forces attack the Alamo and its 189 defenders. Only 16 women, children, and servants survive. Among the slain are frontiersman and former congressman Davy Crockett (who uses his musket, "Old Betsy," as a club in his final hours), Jim Bowie (inventor of the Bowie knife), and a group of Texan and America volunteers. "Remember the Alamo" becomes a rallying cry for Sam Houston's Texan forces.
Feb 23, 1836 - Mar 6, 1836
The Texas Declaration of Independence is enacted, creating the Republic of Texas (otherwise known as the "Lone Star Republic"). This independent state is never officially recognized by either Mexico or the United States. The U.S. government refuses to recognize Texas because it doesn't want to agitate sectional strife. Abolitionists oppose Texas' admission to the Union because they know it will become a slave state. But the U.S. does commence secret annexation negotiations with Texas in 1843.
Apr 21, 1836
In the Battle of San Jacinto, General Sam Houston leads his forces to victory over General Antonio López de Santa Anna's Mexican soldiers. Santa Anna is taken prisoner the following day, forcing him to sign peace treaties granting Texas its independence (although Mexico never formally acknowledges this).
Jan 1, 1842
Whig Party legislators pass a strongly protectionist tariff, one of the few pieces of legislation to survive President John Tyler's veto. The tariff becomes a principal source of factionalism among Democrats.
Jan 1, 1842
Lord Ashburton of Great Britain agrees to a treaty that settles Anglo-American disputes over the U.S-Canadian boundary in the Pacific Northwest.
Jan 1, 1843
Migration to the Willamette Valley in Oregon booms. In less than 20 years, some 53,000 settlers undertake the grueling six-month journey by wagon train along the Oregon Trail from Independence, Missouri.
Aug 1, 1843
Mexican General Santa Anna threatens war with the U.S. if Texas is annexed.
Jan 1, 1844
James K. Polk, Democrat from Tennessee, campaigns for the presidency on an expansionist platform. Polk not only calls for the annexation of Texas, but demands that the British concede to total American control of the Oregon Territory, all the way north to the 54th Parallel (the southern boundary of Russian Alaska). Vowing not to compromise with the British, Polk incorporates the Oregon Territory's northernmost latitude into his famous campaign slogan, "54º40' or fight."
Apr 1, 1844
John Calhoun, appointed Secretary of State under President John Tyler, learns that the prominent Globe newspaper is about to endorse Martin Van Buren for president. In response, Calhoun—who opposes Van Buren—arranges to delay a Texas annexation treaty and make it so proslavery that no one from the North can support it.
Apr 27, 1844
Two letters written by Sen. Henry Clay of Kentucky are published in Washington newspapers. In them, Clay opposes the annexation of Texas because he says it poses a danger to the "integrity of the Union." The Whig party unanimously nominates Clay to serve as its presidential candidate on a platform that does not reference Texas at all.
Nov 1, 1844
Democrat James K. Polk wins the presidency, defeating Whig Henry Clay by a margin of just a 1.4% of the popular vote; he loses his home state, Tennessee, by 113 votes.
Dec 3, 1844
John Quincy Adams, Whig representative from Massachusetts and former president, brings an end to the House gag rule on debate about slavery. Adams has been voted down in each of several previous attempts to repeal the gag rule, but this time, Northern Democrats refuse to assist their Southern colleagues. Seeking to distance themselves from the South to prevent the loss of their states to the Whigs, Northern Democrats don't provide the votes necessary to table the motion. Instead, they help to pass it, 108 to 80.
Mar 6, 1845
Two days after Polk takes office, the Mexican ambassador leaves for home. Diplomatic relations between the two countries are severed over the American annexation of Texas.
Jul 4, 1845
General Zachary Taylor is ordered to "approach as near the boundary line [between the U.S. and Mexico], the Rio Grande, as prudence will permit." Mexico contends that the boundary is marked not by the Rio Grande but by the Rio Nueces, farther to the north. Thus, in Mexican eyes, Taylor's march to the Rio Grande is in fact an invasion of Mexican territory.
Jul 1, 1845
The United States renews its compromise proposal of 49º north latitude for the U.S.-Canadian border line in Oregon Territory. Northwestern Democrats are embittered by this "betrayal" of Polk's campaign promise of "54º40' or fight."
Feb 1, 1845
Congress passes a joint resolution offering to admit Texas to statehood after a long and bitter debate over the question of slavery. The vote is 120 to 98 in the House and 27 to 25 in the Senate.
Mar 1, 1845
In one of the last acts of his presidency, John Tyler signs the congressional resolution offering to admit Texas to statehood. It is an event heralded by most Americans—particularly neighboring Southerners. Mexico vehemently objects, cutting its diplomatic ties with the United States upon receiving the news. Texas formally accepts annexation in June.
Dec 29, 1845
Texas formally enters the United States.
Dec 2, 1845
In his opening message to Congress, President Polk cites the Monroe Doctrine of 1823 (though it will not be called by that name until 1852) to insist that no European colony or dominion shall be established on the North American continent. He wants to keep the British and the French away from California—still a Mexican province—which he covets as a prize for the United States.
Jan 1, 1846
In early 1846, General Zachary Taylor is ordered to advance to the east bank of the Rio Grande river.
Jan 1, 1846
The Sioux Indians, in a petition to President Polk, protest that white settlers in the Great Plains region are driving away the buffalo on which the Sioux depend for food. This forces the Sioux to encroach upon enemy territory in order to find game to hunt, endangering their lives and the welfare of their families. The federal government ignores their pleas for assistance.
Mar 12, 1846
Minister John Slidell is rejected by the Mexican government, but stalls his return back to the U.S. until Congress approves the new Oregon Territory boundaries on April 23rd. That way, the country can focus on the situation with Mexico instead of having to worry about a simultaneous dispute with Britain.
Apr 1, 1846
Congress approves the President's Notice, announcing that the United States will end joint territorial occupation of Oregon with the British after one year, regardless of the state of negotiations between the two countries over the boundary line between the United States and Canada in Oregon Territory.
Apr 25, 1846
A small patrol of American soldiers is intercepted near the Rio Grande river, where they have been stationed. 16 are killed and the remainder captured in a dispute with Mexican soldiers. The incident becomes President Polk's justification for sending a war bill to Congress.
Jun 1, 1846
The British agree to an Oregon boundary at the 49th parallel, as long as Vancouver Island (some of which extends below the 49th parallel) remains entirely in British control.
Jun 14, 1846
Anglo-American settlers in California revolt against Mexican rule and form the Bear Flag Republic, reminiscent of the Texas independence movement. The short-lived Bear Flag Republic accomplishes very little, aside from antagonizing relations between the Anglos and the Spanish-Mexican Californio population.
Jul 5, 1846
Western explorer and mapmaker Captain John C. Frémont (who will become the Republican Party's first presidential nominee in 1856) is named the head of the Bear Flag Republic in California.
Jul 9, 1846
Shortly after landing ships at San Francisco and Sonoma, California, U.S. Naval forces under Commodore John D. Sloat raise the American flag to claim the land for the United States, ending the brief duration of the Bear Flag Republic.
Aug 18, 1846
Gen. Stephen W. Kearny occupies Santa Fe and organizes a civil government for New Mexico, promising a democratic administration. Kearny then moves on to Southern California but is told that Commodore Robert F. Stockton and Lieutenant Colonel John C. Frémont have already conquered the region. Kearny's depleted force is then besieged at San Pasqual and Kearny discovers that Californios have recaptured much of California.
Jan 9, 1847
By early 1847, Kearny has combined forces with Commodore Robert F. Stockton and together they defeat the Californio uprising after battles at San Gabriel and the Mesa. Kearny serves as military governor of the territory until the end of May 1847.
May 8, 1846
The first major conflict of the Mexican-American War, the Battle of Palo Alto (fought just north of modern-day Brownsville, Texas) ends indecisively. U.S. General Zachary Taylor loses nine men and 43 more are wounded; over 200 Mexican soldiers are killed and over 125 wounded.
May 9, 1846
On a Saturday, President Polk convenes his Cabinet and obtains its approval for sending a war message against Mexico to Congress. Four hours after the meeting, the White House receives word that 16 Americans have died in a clash with Mexican troops east of the Rio Grande, providing extra justification for a war decision that has already been made.
May 9, 1846
In the Battle of Resaca de la Palma, American forces under Gen. Zachary Taylor rout Mexican troops led Gen. Mariano Arista, who are forced to withdraw across the Rio Grande.
May 11, 1846
President Polk, who has been planning on declaring war against Mexico for almost a week, sends a war message to Congress on the first working day after hearing of the 16 American casualties near the Rio Grande in Texas. The House is allowed only two hours to debate a bill that calls for 50,000 volunteers and $10 million in military funding. It passes.
Jun 15, 1846
A treaty signed with the British settles the boundaries of the Oregon Territory; the northern boundary of the United States will remain at the 49th parallel, from the Great Lakes to the Pacific. Although a diplomatic success, the Oregon settlement leads to an increase in sectional tensions over slavery and the issue of territorial expansion.
Jun 15, 1846
American Gen. Winfield Scott invades the port city of Veracruz before marching into Mexico City, forcing a treaty that grants the U.S. control of Texas, California, and most of modern-day New Mexico and Arizona.
Aug 8, 1846
In Congress, Democratic representative David Wilmot introduces the momentous antislavery amendment that later comes to bear his name: the Wilmot Proviso. A proposed attachment to President Polk's request for $2 million to fund the war and to buy territory, the proviso would grant the president his funds only if any territory acquired was made free soil. The Proviso splits the Democratic Party, with Southern Democrats unanimously opposing it while Northern Democrats support it by a vote of 54 to 4. In the end, the Proviso passes the House but goes on to defeat in the Senate.
Sep 19, 1846 - Sep 25, 1846
The Battle of Monterrey commences when Gen. Zachary Taylor stations his 6,640 American soldiers north of the city and takes control of the roads. Mexican General Pedro Ampudia and his force of 5,000 are cut off from reinforcements, and Taylor mounts a two-pronged assault. After five days of fighting, Taylor grants Ampudia's request for a parlay and the Mexican forces are permitted to leave with their weapons on September 25th. President Polk is infuriated with Taylor when he learns of these generous surrender terms.
Feb 23, 1847
President Polk, enraged with General Zachary Taylor for allowing Mexican forces to walk away armed after the Battle of Monterrey, transfers Taylor's forces to join Gen. Winfield Scott's invasion of central Mexico at Veracruz. Taylor is left to defend his position near Saltillo with an inexperienced force. To capitalize on the upheaval created by the transition in American troop assignments, Mexican General Santa Anna heads north from San Luis Potosí with an army of 20,000.
At the battle of Buena Vista, Santa Anna's forces break the American line by mid-day before Taylor's reserves under the command of Colonel Jefferson Davis succeed in stalling the Mexican advance. That afternoon, Taylor orders a counter-attack and stalemates the Mexican offensive by nightfall. Over 3,400 Mexican soldiers and about 650 Americans are killed. Although Santa Anna declares the battle of Buena Vista to be a great Mexican victory, in fact, the Americans are left holding the field when Santa Anna's army withdraws.
Mar 1, 1847
President James K. Polk sends Nicholas P. Trist, the chief clerk in the State Department, to Mexico along with Gen. Winfield Scott's forces in order to negotiate a peace treaty with Mexico. Yet Scott's invasion of Mexico City so destabilizes the Mexican government that no negotiations can occur until the ensuing Mexican power struggle ends with a stable administration was in place. Polk tries to recall Trist, but Trist disobeys his orders, staying to sign the Treaty of Guadalupe Hidalgo in February 1848.
Sep 14, 1847
Gen. Winfield Scott leads a victorious American army into Mexico City. American occupation of the capital throws Mexico into crisis; Santa Anna resigns as president, leaving the Mexican government teetering on collapse. This prompts some die-hard expansionists in the U.S. to propose annexation of the entire Mexican republic.
Dec 1, 1847
Preparing for his annual message to Congress, President Polk plans to deliver a threat that more land cessions—in addition to California and the Southwest—will be necessary if Mexico protracts the war any further. In the end, he abandons such strong language to avoid inflaming political opinion.
Jan 24, 1848
James Marshall discovers gold at Sutter's Mill, along the American River near Sacramento, California. Had the Mexicans discovered California's gold earlier, history may well have turned out much differently. There would have been a much larger Mexican presence in California, possibly enough to withstand Manifest Destiny.
Feb 2, 1848
The Treaty of Guadalupe Hidalgo ends the Mexican-American War. California, Nevada, Utah, most of New Mexico and Arizona, and the disputed regions of Texas are all obtained by the United States in the largest single land acquisition since the Louisiana Purchase of 1803. All told, some 55% of Mexico's prewar territory is transferred to American sovereignty. President Polk actually wants even more land, but consents to the settlement when faced with growing public hostility to the war.
Feb 21, 1848
John Quincy Adams, staunch opponent of slavery and the only president to serve in Congress after his presidency, is struck with a fatal cerebral hemorrhage in his seat on the floor of the House and dies two days later, the same day that the Senate receives the Treaty of Guadalupe Hidalgo. Congressional business is suspended until after his funeral.
Mar 10, 1848
The Senate ratifies the Treaty of Guadalupe Hidalgo.
Aug 1, 1848
Antislavery members of the Whig and Liberty parties join to form the Free Soil Party, which opposes the expansion of slavery into the newly acquired western territories. The party nominates former president Martin Van Buren as its candidate in the 1848 election; he wins 10% of the vote, splitting the Democratic base and facilitating the election of Mexican-American War hero and Whig candidate Zachary Taylor to the presidency.