George Mason combined management of his Virginia plantation at Gunston Hall with local government and political writing. He served in the colonial House of Burgesses and participated in county institutions while avoiding a continuous career in high office. Opposition to British taxation and imperial measures drew him into the revolutionary movement. The Fairfax Resolves of 1774, developed with George Washington and others, expressed a program of resistance through constitutional argument and economic pressure.

In 1776 Mason played a central role in drafting the Virginia Declaration of Rights and the state's constitution. The declaration identified rights inherent in people and principles for government, including representative authority and protections relating to criminal justice and expression. Its language influenced subsequent American statements of rights. The final version did not establish equal rights in practice for enslaved people or women. Mason's own wealth and household depended on slavery, exposing the limits of the universal language he helped formulate.

At the Constitutional Convention in 1787, Mason contributed actively to debate over the structure and powers of the new federal government. He objected to the absence of a declaration of rights and criticized provisions he believed would endanger liberty or favor particular interests. He condemned the continued slave trade but remained a slaveholder and did not propose immediate general emancipation. His objections also included the balance of representation, executive power, and congressional authority over commerce.

During Virginia's ratification debate in 1788, Mason joined opponents who sought changes before accepting the Constitution. Ratification nevertheless proceeded, accompanied by recommendations for amendments. The later federal Bill of Rights addressed some concerns he had emphasized, though it was shaped by several states' proposals and James Madison's work. Mason retired to Gunston Hall and died in 1792. His career was influential through constitutional drafting and principled opposition rather than national executive office. Assessing his contribution requires retaining both his insistence on protections against concentrated power and his participation in a slaveholding society. The contrast between proclaimed natural rights and the people excluded from them is part of the constitutional history he helped create, rather than an incidental feature of his private life.