Taylor was an old general, a hero of the war with Mexico who, before he ran for president, had never once voted and who was semi-illiterate (which is not to say he was stupid - he just had never cared to learn until it was a bit too late).
He was a slave owner. Louisiana is officially considered his home state, it's where his small absentee plantation was. He was born in Virginia. Southerners believed themselves to be in safe hands with him.
At the time of the treaty of Guadalupe Hidalgo in 1848, the peace treaty with Mexico in which the US annexed New Mexico, COlorado, Utah, Nevada, Arizona and California (roughly), there was agitation in the North for the "Wilmot Proviso". This stated that the treaty be ratified only with a rider declaring the entire area as free-soil (ie, banning the importation of slaves into it). It was defeated at the time.
Now, the new president Fillmore, a practical, unpolitical man with a greater respect for Mexicans and Southwestern Indians than was common for Yankees at the time, saw that these large territories as future bones of contention should the question of slavery there not be settled quickly. He also saw that the inland SW wasn't suited for chattel slavery anyway, and unless most other people he was ready to acknowledge that it already had the "50.000 inhabitants excluding Indians not taxed" necessary for admission as a state, although few of them spoke any English.
He therefore moved to admit two giant free states, California (also including Nevada) and New Mexico (roughly the other four). That, of course, was from a Southern perspective even slightly worse than the original Wilmot Proviso. Worse, this came from "their" president! They felt betrayed and were quite angry. Some actually threatened secession.
And then he died, somewhat mysteriously. There is an old conspiracy theory that he was poisoned with arsenic. However, about ten years ago his decendants had him exhumed to find out for sure, and it was proved that he was not.
SOuthern radical ringleader John C Calhoun died about the same time, the proposal was dropped (though California in its modern shape was admitted to the union, as a free state), there was a number of compromise measures pushed through congress by Henry Clay, who died soon thereafter, and the threat of secession receded for some years.
Now, if Taylor had lived and Calhoun had died, I guess civil war would have been averted for the moment, and would have broken out at the time it actually did, but the Taylorite states would probably have come into existence. That has implications both for electoral history (fewer states, question of who would have won that giant New Mexico when) and for the settlement history of the US. Would the Mormon dominance in utah have come to pass if Utah had been a part of a Hispanic state?Would mass immigration into Arizona and New Mexico have set in earlier, quickly destroying the state's hispanic majority, or would it have come later or even never? Might Spanish now be an official language of the US alongside English?
Where does Fillmore suddenly come into it, do you mean Taylor all the way?
