When the US was founded, what gave the Southern States an advantage? Why would it give them an advantage?

What gave them an advantage is economic prosperity due to rich soil and development of plantations based on slave labor. Many profit was accumulated from crops (tobacco) and also cotton. Later on in the 1800s when Eli Whitney created the cotton gin it created a boom in the slave industry and increased largely by 71%. After that the tool allowed mass production in textile industries.