Because they needed more land, as they were growing cotton, which wears out soil really quickly. With the invention of the cotton gin, they could make much more, so they needed more slaves and more plants, and therefore more land.
ALSO: so they could keep enough strength in the senate to protect southern interests
the admission of kansas into the union
The south was based off of farming. They had a small scale of land and a low population. They wanted to reach new territories to help promote slavery and farming.
It didn't expand west. The Kansas Nebraska Act made sure that it didn't go further. California came into the union in 1850 a free state. There never was slavery in the western states.
The whigs from the North were known as Conscience Whigs and those of the South were known as Cotton Whigs. The ones in the north opposed slavery except for the factory owners, which liked slavery die to the cheap cotton. the Southern Whigs supported slavery and wished to expand it into the territories.
The topic of the Lincoln-Douglas debates mostly concerned the extension of slavery into the US territories. Douglas believed that the territories should decide for themselves whether or not they wished to have slavery. He felt that power should reside at the local level and should reflect the wishes of the people. Lincoln stated, "A house divided against itself cannot stand." Lincoln believed that slavery must be dealt with as a moral wrong and that only the power of the federal government could extinguish slavery.
maintain political power by ensuring that new states admitted to the Union would allow slavery, preserve the economic benefits of slavery for the southern plantation system, and protect the social hierarchy that relied on slavery for labor. This desire to expand slavery into western territories ultimately fueled tensions between the North and South, leading to the American Civil War.
cuba and nicaragua
David Wilmot wanted slavery prohibited in territories acquired from Mexico in order to prevent the spread of slavery into new territories, as he believed that allowing slavery to expand would only further entrench the institution in the United States. This proposal, known as the Wilmot Proviso, aimed to preserve the western territories for free labor and was part of the broader political debates surrounding the expansion of slavery in the mid-19th century.
The Confederacy did not want to abolish slavery. In fact, they wanted to expand slavery into the new territories of the US.
the admission of kansas into the union
If slavery was not permitted in the Mexican cession, pro-slavery southerners ambitiously sought to expand their slave holding territories into Latin America. They created the Ostend Manifesto that called for the purchase and annexation of Cuba. If Spain refused to sell, they favored going to war with Spain.
It revived disagreements because the Northerners believed Southerners wanted to expand slavery to new lands.
Pro-slavery means that you favor slavery, & want it to stay.
So they wouldn't keep getting outvoted in Congress
Consider this: Exactly which "people of those territories" wanted expansion of slavery. Definitely not any of the black people. Actually, nearly all the lobbying for slavery came from people living in the South who were anxious to gain more power in the House and Senate for their cause.
Some believed in expansionism and Manifest Destiny. Some wanted to expand slavery.
Manifest Destiny is Polk's belief that the United States was destined to own the Western territories and expand over into the Western unorganized territories. Check out the related link for more information.