Why was slavery important to the south in 1800s?

The Souths aristocratic social culture was largely built on slavery. However, one must consider that the entire nation profited greatly from the slave trade. during the beginning of the Industrial revolution, slave holders in the South were more considered with increasing slavery than with building up cities and strengthening infrastructure. This created a large discrepancy between the North and the South. The south was reliant on imports from Northern factories for many goods and services. Wealthy planters in the South enjoyed the class distinctions and the lack of upward mobility that slavery afforded them. Even poor whites that were non-slave holders could not compete for political power with the wealthy planters. With the invention of the cotton gin in 1799, formerly unusable cotton was able to become a huge wind fall for the South. Cotton production increase 800% in a decade and the need for slaves increased with it. Southerners ignored the fact that an economy reliant on one agricultural crop was not sustainable for lengthy periods of time. They also failed to heed that cotton was a crop that depleted the land of its nutrients. Southern gentility was focused on ensuring that slavery could be carried into new american territories across America. Most Republicans were wholly against this practice and wanted to enact "free soil" legislation that would prevent the spread of slavery into territories where it did not exist. Such policies would effectively kill the southern economy, that was still dependent on the manual labor of slaves for its production of cotton, rice, indigo, etc. Hope this helps!

It was dependable labor (but not cheap) for an industry that was very labor intensive.

It was pretty important to the millions of people in the south who were slaves, because it meant they couldn't live their lives as they chose to, and it often meant they could be legally tortured and killed.

"The South" - presumably the southern part of the USA.

Slavery was important in many parts of the world in the early to mid 1800s, and still continues in some parts of the world. Quite likely something you are wearing at this moment was made in slave-like conditions.

It was the foundation for Southern culture prior to the American Civil War.

The two most important crops in the Southern agrarian society were tobacco and cotton. Cotton was King in the South - 80% of the crop went to England.
Both crops were labor intensive to plant, maintain and harvest.
Slaves were not cheap; but they had one advantage over mechanical equipment: they could make more slaves.
A peculiar institution indeed.

Unpaid labor.

"The obvious answer is that slavery was the basis of the southern economy. Most of the wealth of the South came from the crops that the slaves grew."

It helped the Northern Union Plantation owners make more Money with free Labour