The ideas of the social contract, natural laws and natural rights, and separation of powers, are all found in our Founding Documents, like the US Constitution and the Declaration of Independence.
The founding fathers, when drafting the constitution, were mostly influenced by the English/Bill of Rights and the Magna Carta, more specifically the idea of the separation of powers, that were derived from the two articles. They came up with the separation of powers as to have a separate legislative and executive branch, so the new government isn't so easily corrupted.
