Freedom in the 1750's is primarily based the availability of new opportunities granted from immigrating to America. New colonists had opportunities not present for them back in England. Slaves, on the other hand, were rarely if at all granted any rights.
During the Revolutionary War, the concept of freedom was based upon becoming liberated from England and becoming a separate nation. The air was filled with talk of independence and the streets were lined with propaganda.
Following the Bill of Rights and the Constitiution, the idea of freedom was expressed by the most well know freedoms granted in the Constitiution: Freedom of Speech, Religion, and the Press.
Freedom in the early to mid 1800s was spiraled around the idea of economic dominance, primarily the establishment of factories and industrial sectors like Slater's Thread Spinning Factory.