Locke's contribution to American political thought was the way he formulated liberal thought. In Locke's thought, men have intrinsic moral worth. They are capable of being their own moral agents, thus capable of self rule. They are equal, and they are free from claims of divine right to rule. This is liberalization, meaning that traditional ruling systems of personal power, justified by divine right, are rejected. The political power is opened up to the people, and "opening" is what liberalism means. When the people have the sovereign power, power becomes a public matter. In Latin, that is "Res Publica." Self rule is a republic. The power of the people is delegated to representatives to speak on their behalf so people have a stable environment in which to pursue economic activity.
Since men are free and equal, then, they have natural rights. These are life, liberty, health, and pursuit of property. Property is the source of political power, hence freedom, and this comes with the obligation to defend it so you don't lose that liberty. You cannot alienate your natural rights. You must set up a system to limit encroachments and preserve your rights. So you must have the ability to protect your freedom, which is the right to pursue property. Jefferson cribbed this line but he changed "property" to "happiness."
