Montesquieu: separation of powers (Constitution, 3 branches of US gov w checks and balances on each other's powers)
Locke: Natural Rights of Life, Liberty and Property (Declaration of Independence), concept of a Social Contract: government exists to protect the rights of the people and requires "consent of the governed," if it fails to protect those rights that's tyranny and the people can rise up and overthrow it (literally the entire premise of the American Revolution)
