Now, you've asked a really huge question, and I'm going to start by providing background and speaking quite broadly. I'm most familliar with the Upper South, but I'll try and say something about the Cotton South. Please feel free to ask further questions and I'll try to dial it in more.

Basically, the southern colonies transitioned to a cash crop economy very, very early in their history. This starts in Virginia colony, which was founded initially for the purpose of extracting mineral wealth: gold, silver, jewels. The English experience in the New World, prior to that time, had centered on the Caribbean, where they had regularly raided going back into the 16th century (and which would continue to be the focus of their attention through most of the 17th century). They were familiar with the great wealth Spain had been gleaning from mines in Central and South America and hoped to get in on the action. Agriculture was not in their minds at this point. This is borne out by the occupations that were brought over to Jamestown initially: goldsmiths, military adventurers, gentlemen, and the like.

Within a matter of a few years, the remaining colonists (a lot of them died, and new ones were brought in periodically, most of whom also died) realized that Virginia is a really awful place to go looking for precious metals and stones, but a good place to grow tobacco. This had been almost exclusively a Caribbean crop prior to this time. In 1609, John Rolfe brought Spanish Varina tobacco from Bermuda to Virginia and in very short order the entire colony had been structured around the production of it. Virginia, in the 17th century, was tobacco.

The period 1670-1700 represents the zenith of the tobacco monoculture in the broader Chesapeake region of Virginia and Maryland. Never again was tobacco quite so profitable to grow. A variety of factors contributed to this, among them, depletion of soil, trade disruptions, rising costs of production, and diminishing yields. Moving into the 18th century, planters were forced to diversify into additional crops, and in the upper south a three-part agricultural system developed. Corn was grown, largely to feed animals and slaves, wheat was grown, both for consumption and export, and tobacco continued to be grown. In this way, they were able to largely maintain the high profits they had achieved in the 1670s and 1680s through tobacco alone. Diversified agriculture continued to be the rule in the Upper South through the Civil War.

The opening of the western lands coincided with an economic situation that made the growth of cotton very attractive to the new settlers. Indigo and tobacco prices were very poor in the 1790s. But cotton commanded quite good prices, and the Gulf Coast South, especially the Mississippi Valley, was a great place to grow it. The spread of the cotton gin to the Mississippi Valley in 1795 made it much easier to process and thus more profitable. Improved strains of cotton were bred which produced more and grew better in the soil of Louisiana, Mississippi, Alabama, and Georgia. A complex system soon developed. Banks lent money freely (arguably, recklessly); slaves were brought in from Virginia, Maryland, North Carolina to grow it; agents in Natchez and later Vicksburg and Port Hudson shipped it down the river on barges and, later, steamboats; and in New Orleans it was purchased by Northern, but especially British and French, merchants.

By this point, cotton was fully established in the Deep South, for better or worse, and quite often for worse. Following the Panic of 1819, the 1820s were generally a very gloomy period marked by falling prices and a tightening of credit. Cotton was hardly grown at all in North Carolina, Virginia, Maryland, and Kentucky, which maintained more diversified economies and, especially in the mid 19th century, made much greater progress to industrialization.

Philip D. Morgan. Virginia's Other Prototype: The Caribbean.

Kathleen M. Brown. Gender and Race in Colonial Virginia.

Lorena S. Walsh. How Tobacco Production Shaped Slave Life in the Chesapeake.

Adam Rothman. Civilizing the Cotton Frontier.