The term Manifest Destiny was first used by John O’Sullivan in his magazine American Review, but it described a feeling that was common among many Americans, especially members of the Democratic Party. This was the belief that some higher power such as God wanted Americans (His chosen people) to expand over the North American continent. People thought of taking both Mexico and Canada. The feeling described by the term Manifest Destiny had spread across America in the early Forties of the Nineteenth Century. In today’s parlance we would say that Manifest Destiny was a meme, that the idea had gone viral.

Here is a chart for Spring Equinox of 1843 showing the outer planet Uranus beginning the transit of the IC of the United States chart, a position that it would occupy for the next couple of years. The IC represents the base or foundation of the person represented by the chart, in this case the United States. This point is the furthest submerged, and transits to this point are long lasting and not easily recognized, the effects seem almost to come out of nowhere. In this case, after the crisis represented by the transit of Uranus over the MC 42 years earlier, to be discussed later, America was beginning to feel sure of itself, and this urge to expand was just a manifestation of this new found feeling of being a unified country.
In the election of 1844, the original dark horse candidate James Polk, a protégé of Andrew Jackson, was finally nominated to head the Democratic ticket for President, opposing Henry Clay of the Whig Party; that party had won the previous election but that President had died immediately upon taking office. Clay ran on the expansion of American infrastructure whereas Polk ran on expansionism, to bring Texas and Oregon into the Union. He also wanted to bring California into the United States, but this was not mentioned at the time. Polk won.
Three future presidents served in the Mexican American war: Ulysses S. Grant, Franklin Pierce, and the next president, Zachary Taylor. James Buchanan, the President after Pierce and before Lincoln, was Secretary of State under Polk, and Abraham Lincoln was a Whig Congressman under Polk.
The war with Mexico was unique up to that point. America had fought wars before, with Great Britain and mostly with Indians, but this was different. The Indians were somehow already living on land that was considered United States, and they just had to be convinced to allow US settlers to live on the land that they somehow occupied. And the British were the former masters of the United States and they had to be prevented from continuing to tell the country how to behave. But Mexico was a separate republic, an the US had no right to their land.
After his election, Polk sent Taylor and United States troops to a position just north of the Rio Grande river, which he considered the northern border of Mexico and thus the southern border of Texas. However, most people in the United States who were not Democrats as well as the Mexicans and Texians (their preferred name) thought the border to be the Nueces River many miles north of the Rio Grande.

Here is a chart for Taylor’s advance over the Nueces River on February 3, 1946. This was an act of aggression that many recognized at the time. The tightest aspect is Pluto sesquiquadrate the US Ascendant, recalling the tight Pluto semisquare Ascendant in the natal chart. Pluto can be seen as aggression and urge to dominance. But notice also the approaching Saturn Neptune conjunction of the US Moon. This is not a good sign for a positive reaction at home, as we’ve explored before. Presidents should know better than to schedule a war any time a Saturn Neptune hard aspect is coming up.
This action was not well received by the Mexicans or Zachary Taylor either. Taylor was a Whig and like most Whigs was against the war with Mexico, which he thought was patently illegal. But he had his orders. The Mexican army attacked Taylor’s troops,which they saw as invaders, and Polk had his casus belli. The war lasted for two years, and proved to be longer and more bloody than anyone had imagined. Does that remind you of a more recent war? As an outcome, Polk was able to get the state of California, which had long been his goal, as well as most of the new states of Arizona, New Mexico, and Nevada well as small parts of other states. And the United States got Utah, which had been settled by the Mormons after they were chased out of Indiana. In fact, to help the war effort Mormon troops fought with the enlisted men and the volunteers

Here is the chart when the Mexicans attacked the Americans, which is the putative start of the war, even though it had really stated with the previous action. We see that this is close to the Mars Return of the United States, when Mars returns to its natal position. A Mars Return would indicate a time when one is especially martial. But note that that Saturn-Neptune conjunction is on the US Moon quite tightly. Saturn Neptune indicate that what was once thought to be a good idea is no longer believed to be, and since it is on the US Moon, the people of that country deeply felt that. And in fact by the fall of 1846 enthusiasm with the war was already waning, as news of the atrocities committed by the US troops reached the Americans.
Here are the charts of both James Polk and Zachary Taylor, who succeeded him as President of the United States.

The time of Polk’s birth is supposedly from his diary, so it should be accurate. He has Jupiter rising, suggesting that he gives a lot of his energy to the world, that he is optimistic. And in fact he had a great difficulty in delegating tasks to others when he was President and would not take vacations though many, including his wife, begged him to do so. On nomination he assured his followers that he would serve only one term, which was fortunate since he died a few months after leaving office. He was also a Scorpio president, Scorpio being ruled by Pluto (an unknown planet at the time). Another well-known Scorpio President was Theodore Roosevelt, also known for his aggressive behavior.

In the chart for Zachary Taylor, “Old Rough and Ready” (he did not like to “dress up”), the second and last elected Whig President, shows Pluto rising and Mars at the Midheaven, with most of his planets in the East, that is the left hand side of the chart. The positions of Pluto and Mars are most appropriate for a military commander. Planets in that hemisphere indicate a person largely in control of their own destiny, someone whose own actions determine their outcome in life.
The troops sent into Mexico were composed of regular US troops, mostly lower class people who needed a job the military could provide, and volunteers, who were generally of a higher class. About two-thirds of the troops were volunteers, and there was much ill-feeling between the two groups. Many of the volunteers brought “servants” with them, mostly slaves. The volunteers were also not nearly as well trained as the regular army troops. There were also many atrocities committed by the volunteers against the Mexicans, and as Fall of 1846 approached, people in the United States, and then in London, began to hear about these atrocities . General Taylor did not like the volunteers, but Polk sidelined him by sending in another military commander who got two-thirds of the troops. Polk was afraid that Taylor was getting too popular as a military leader and might run for President (which he did) as a Whig, which Democrat Polk did not like.
A majority of the volunteers came from slave states, but the largest source of volunteers was Illinois. While technically Illinois was free state, southern Illinois bordered on the slave state of Kentucky and Illinois citizens owned many slaves. Also, Illinois citizens were in general great believers in Manifest Destiny.
Originally Polk, and many of the troops serving in this war, were for taking more of Mexico that they actually did. Once the troops entered Mexico, they saw how barren the country was, and were upset at the backwardness of the Mexicans, who they considered to be barely above Indians or slaves.
When the vote to authorize the invasion took place in Congress — this was still a primitive time when they actually followed the Constitution’s requirement that the Congress declare war — although the Whigs were against the war, many of them voted for it. They remembered that once there had been the Federalist Party that had strongly opposed the War of 1812, and as a result that party was no longer in existence. The Whigs did not want to follow the same path. However, some Whigs followed their conscience and voted against the war; these were called the “Immortal Fourteen”, amongst whose members was John Quincy Adams, who had been a President twenty years before and was a strong abolitionist voice in the Congress. But the war resolution passed.
After the War, most people expected the new territories acquired to be settled by slave owners, thus making slave states the majority in the country. Certainly Polk, a slave owner from Tennessee, expected this. But an abolitionist congressman from Pennsylvania by the name of David Wilmot introduced what was called the Wilmot Priviso, that prohibited slave owners from making any states from the new territories slave states. This controversial bill was introduced into many sessions of Congress, and the controversy about the status of these new states was one of the things that led to the Civil War.

Here is a chart for the first introduction of the Wilmot Proviso. Again there is the Saturn-Neptune conjunction on the US moon, but now is is opposed by Mars (War). Venus (Peace) is conjunct the US Sun (Government) and Jupiter (Expansion) is opposite the US Ascendant.
There were embedded US reporters with the troops in Mexico, and often their reports reached Polk before diplomatic reports did. These embedded reporters were uniformly for the war until they began to see the atrocities committed by the American volunteers against the Mexican people.

The biggest massacre was at a cave in Agua Neuva. Here is an event chart for that massacre. Over two dozen Mexican men were butchered in front of their wives and children, and many were scalped. American soldiers had learned from their wars with Indians. In this chart the tightest aspect is the opposition between Mars and Pluto – Pluto again playing a dominant role – and this aspect was tight no matter the time of day, and there is a waning Sun-Mars conjunction. Ebertin says of Mars-Pluto “Superhuman power, force, brutality.” I call it, somewhat jocularly, as the aspect of the mass murderer, and in fact the killer at Virginia Tech had these two planets in conjunction.

After a long battle in Mexico City, General Scott won and the American flag was raised over the city. Here is the chart for that flag raising. Venus rising is a significator of peace, but peace was not forthcoming since the US troops were wrecking the city and raping the women, so the citizens of that city were not too happy with the America presence and continued to battle them. This was America’s first experience at occupying a foreign country, and it was not popular with the Mexicans who fought back with stones, result in mass killings by the Americans.
Many in the Northeast were opposed to the war, such as Ralph Waldo Emerson and Henry David Thoreau; in fact the famous confrontation between the two men happened during the war. Thoreau was in jail for refusing to pay his poll taxes to support the war. But many Americans were for the war, at least initially. For example Walt Whitman, then a newspaper editor in Brooklyn, did not come out against the war until he realized that it was meant to increase the number of slave states. That change of opinion got him fired from his job.
Zachary was elected a a Whig President in 1848, following Polk who died months after leaving office. The story has it that Taylor died after eating cherries and milk on the Fourth of July while raising money for the Washington Monument which was then being constructed. But some think that he was assassinated by Southerners, who were not happy that he wanted slavery outlawed in the new states gotten from Mexico. This theory was propounded by Michael Parenti in his book History as Mystery, and details of this theory can be searched for on the Web. In 1850 there was a Uranus-Pluto conjunction and many Southerners wanted to leave the Union. This crisis was defused by the passage of Henry Clay’s Compromise of 1850, but it was a forerunner to the final act of succession ten years later. This Comprise had been opposed by Taylor, but his death allowed the Compromise to pass, in several bills, which included the hated (by Abolitionists) Fugitive Slave Act, which required runaway slaves to be returned to their “owners” no matter where they were captured.

In this chart for the death of Taylor – it took him several days to finally succumb to his mysterious aliment – we see the Uranus-Pluto conjunction that marked 1850 square his Ascendant and in this Third House, along with Saturn.
The Treaty of Guadalupe-Hidalgo finally ended the War long after Mexico City had been captured. While many Americans wanted to take all of Mexico, Polk’s negotiator did not think this was a good idea, and because of the distance involved and the lack of good communications – the telegraph had only recently been introduced – a compromise was reached in which the US government paid money to the Mexican government in exchange for most of everything that is now the Southwest United States. This is called the “Mexican Cession” but as we have seen it was far from voluntary.

In the chart for this peace treaty, we can see that the Saturn-Neptune conjunction has long passed. Saturn now squares the US Ascendant and Uranus opposes the US Saturn. The country did not get all that they wanted from Mexico, and further difficulties were in store for the country as the issue of slavery became more pronounced over the following decade. The tightest aspect is Jupiter sesquiquadrate the US Moon, and it is also conjunct the US Sun. The expansion (Jupiter) of the US was mostly complete with this treaty (a compromise with Great Britain previously in the Polk term had resulted in the Oregon territory south of the 49th parallel being included in the United States) and the present day continental US took shape.