Southern leaders were concerned because cotton was the only major crop that was being grown. If a disease, natural catastrophe, etc. destroyed the cotton, the South had no other crops to maintain their economy. They relied solely on cotton.
By issuing the Declaration of Independence, adopted by the Continental Congress on July 4, 1776, the 13 American colonies severed their political connections to Great Britain. The Declaration summarized the colonists' motivations for seeking independence.
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In the 430s, Roman Empire's declined power over ports in the Southern of their territory is attributed to the invasion of the Vandals or the East Germanic Tribe. The Kingdom of Vandal is led by Gunderic who unified various tribes in conquering the territories especially those near the sea.