The declaration was a laundry list of affronts to the colonies by King George III, wherein Jefferson et.al. argued that since the monarchy did not treat the colonists like other Britons, the colonists had the right to form their own sovereign nation. It was also intended to justify this action to other monarchies to prevent them from helping Britain retain the colonies under the doctrine of Intervention. So it helped to justify the war domestically and internationally.
The 14th amendment did much to educate and provide jobs for newly freed slaves following the end of the civil war.
The main factor that led to the development of the four major river valley civilizations was its closeness to rivers, which was a food source, its flooding allowed for fertile soil, allowed easy transportation and cities near them were easier to defend.
The fact that fewer people had to dedicate to the production of food allowed some of them to develop other activities, such as the construction of building and cities, metal working, trade and social organization. This led to a social division, the ones that worked and the ones that ruled, creating intricate systems of governments and religions that ideologically sustained those in power.
It was because he ignored the wishes of the american Admin of Fighting Spain