I hope the reader has brought a lunch. We may be here a while. :)

How influential to the nation was the California Gold Rush? Relatively big. I'll inevitably miss things and only scratch the surface, but here's go at it.

News of the discovery populated California fast enough that it had to have a government yesterday. The population growth more than justified statehood. The Californians duly got together a constitutional convention, wrote their constitution, and sent it off to Washington expecting admission into the Union. Big deal for California, but what's that to do with the nation? Well, the Californians voted to become a free state and this slammed them hard into a debate that had been going on for the last few years. To explain that, we'll have to go back in time and across the map a little bit.

The Texas Republic, largely populated by Americans, had won its independence from Mexico back in the 1830s. The Texans in charge at the time wanted admission to the United States and sent to Washington about it. They were, until rather recently, Americans. They were right next to the United States and rather far from the government in Mexico City. Why not let them in?

Well, Texas had slavery. In it, many Americans saw slavery's future. A Texas in the Union meant more land open to slavery, which had been excluded from most of the Lousiana Purchase by the Missouri Compromise, and thus most of the remaining unorganized territory that could become states in the future. This excited antislavery and proslavery Americans alike, if for opposite reasons.

But on the international stage, Mexico hadn't quite accepted Texas independence. It still claimed the territory, practical control of it or not, and annexation would invite war. For that matter, the Texans didn't have practical control over most of the land they claimed either. Even if the two parties could reach some kind of settlement, by no means a sure thing, they'd have a disputed borderland. The Texans claimed the Rio Grande and the Mexicans insisted on the Nueces, a good hundred miles further north.

Looking at all of this, the Democrats' and Whigs' leadership alike spend a decade in general agreement that Texas wasn't worth it. Things eventually broke loose amid some controversy. John Tyler couldn't get the 2/3 of the Senate he needed to sign on for a proper annexation treaty, so he decided to try it with a joint resolution of Congress that would only require a simple majority of both chambers. Tyler hoped that the annexation would save his political career, but after lucking into the job through William Henry Harrison's death (People called Tyler His Accidency.) and being the odd man out as a southern states rights guy among the somewhat more nationalistic and northern Whigs, plus a turncoat from the Democracy, he had few friends in Washington. Obivously I'm skipping over a lot of details here, including some complicated internal politics, but this is a question about California and it would do to get back to that.

This led to the expected war with Mexico in 1846. The United States prevailed and collected not just all the land Texas claimed, but also everything in the modern continental US except the portion of modern Arizona and New Mexico below the Gila River, California included. Before the war was even over, controversy erupted over what to do with the land that the nation expected to collect. Some Whigs wanted just Texas and maybe some kind of railroad concession out to San Francisco. The Democrats, who now had James K. Polk in the White House, wanted rather more. In fact, when the war seemed to be going well, they started getting even greedier. A few Democrats even implausibly dreamed of annexing all Mexico. The more numerous and grounded thought about claiming Mexican states south of the Rio Grande.

As of the Missouri Compromise, all the territory in the nation had its future spoken for. It would, in time, come into the Union as either a slave or free state. Accepted practice was to bring in states in roughly contemporaneous pairs. Why? Way back at ratification, the sections had roughly equal populations. That meant roughly equal representation in the House of Representatives. Northern Congressmen could get all the wild emancipation ideas they liked at home, but Southerners could frustrate them in Washington. The greater population growth of the North changed that. As the North's population took off, so did its power in the House. With sectional parity in the popular house going out, it became even more important that the South keep its sectional parity in the Senate. If it didn't, even if it only fell a state or two behind, each loss would make the next one come all the easier. Eventually, the House and Senate together might assembly 3/4 of the states and pass some kind of constitutional amendment to abolish slavery. Even if they didn't, it would be easy for them to engage in all kinds of mischief that undermined slavery, directly or otherwise.

What kind of mischief? David Wilmot (D-PA) had an idea. Wilmot attched a rider to an appropriation for negotiating the peace with Mexico. It repeated the nation's very first antislavery law, the Northwest Ordinance, applying it to any land gained from Mexico:

That, as an express and fundamental condition to the acquisition of any territory from the Republic of Mexico by the United States, by virtue of any treaty which may be negotiated between them, and to the use by the Executive of the moneys herein appropriated, neither slavery nor involuntary servitude shall ever exist in any part of said territory, except for crime, whereof the party shall first be duly convicted.

This can easily be misunderstood. Without context, you can get the idea that Wilmot is some kind of abolitionist. The man himself set the record straight:

Is there any complexion of Abolitionism in this, sir? I have stood up at home, and battled, time and again, against the Abolitionists of the North. I have assailed them publicly, upon all occasions when it was proper to do so.

Wilmot favored keeping slavery out of the future Mexican Cession, except for Texas which he took as a fait accompli, because Mexican law had excluded it. Thus, by his reading of the situation, that soil was free until someone voted slavery in. He opposed that, but he made it very clear that this didn't come out of any humanitarian concern for black Americans:

I have no squeamish sensitiveness upon the subject of slavery, no morbid sympathy for the slave. I plead the cause and rights of white freemen. I would preserve to free white labor a fair country, a rich inheritance, where the sons of toil, of my own race and own color, can live without the disgrace which association with negro slavery brings upon free labor.

Wilmot's racism aside, wouldn't we expect an instant southern freakout? Maybe, but we didn't get one. Southerners disagreed amongst themselves about how much they really had to gain in the Mexican Cession. Most of the land was desert. They had a lot of Texas yet to develop, plus virgin land in Arkansas. The only good land seemed to be in California, on the far end of the desert and thus hardly a prospect for instant development. Getting to California would require a lengthy trip through dangerous, hostile land full of American Indians and peppered with Mexicans, or a longer but faster and safer trip by way of the Isthmus of Tehuantepec, southern Nicaragua, or even all the way down to Panama. Not exactly the easiest place to get slaves to. That concern help animate dreams of a Pacific railroad, which are out of the scope of the question. I've written about those a bit here, if anyone's curious.

The proviso did not go away. It kept coming up and Southerners needed every senator to veto it when it reached the upper house. One traitor to the section, of the kind that had managed to pass the Missouri Compromise and would pass future compromises, and they would fail.

That traitor could come in the form of Cassius Clay of Kentucky (the one whom the future Muhammed Ali was ultimately named after), or a follower, who led an antislavery movement in that slave state. If Clay's movement prevailed, then Kentucky could have an abolition senator. He posed a threat both because Kentucky had elected a soft on slavery senator before, his cousin Henry Clay, and because Clay tried to make common cause with the poor whites of Kentucky. Planters in every slave state relied vitally on the support of poorer whites to keep their slaves. Kentucky's, living outside the cotton belt and in a fairly narrow plantation band that slowly bled slaves into the Lower South Cotton Kingdom as well as leaking those that stole themselves across the Ohio River, could see a possible demographic transition in their future.

Clay and his small movement advocated for that openly. Get the slaves out, bring free labor in, and Kentucky would prosper. The state already had a law on the books limiting slave imports, though it was repealed in 1849. At the same time, the state agreed to a constitutional convention. Clay and his movement hoped to use it to get the old import ban back. Some hoped to go farther. They didn't get their wildest dreams, but the eventual proslavery settlement contemplated a future whitening of Kentucky as slaves bled away south and west until the institution was no more. If Kentucky didn't supply the traitor to his section and race, then some other border state might.

(more to follow)