Southerners also defended slavery because it was connected to property rights as enshrined in the US Constitution.
The US constitution allowed for certain laws to be amended over time and the Bill of Rights gave US citizens certain rights which could never be taken away from them, if they are, they can overthrow the government.
No, it is false that sandstorms frequently happen in Mediterranean and tropical climates, since sandstorms typically occur in areas that have a lot of sand in the center of the country, such as in the Middle East and Africa.
The Declaration of Independence was signed July 4th, 1776.