His writings, including substantial portions of the Fairfax Resolves of 1774, the Virginia Declaration of Rights of 1776, and his Objections to this Constitution of Government (1787) opposing ratification, have exercised a significant influence on American political thought and events.

During the American Revolutionary War, Mason was a member of the powerful House of Delegates of the Virginia General Assembly, but to the irritation of Washington and others, he refused to serve in the Second Continental Congress in Philadelphia, citing health and family commitments.

Joseph Horrell, in a journal article on Mason's court service, noted that he was often in poor health and lived the furthest of any of the major estateholders from the Fairfax County courthouse, whether at its original site near today's Tyson's Corner or later in newly founded Alexandria.

He also served as a trustee of Dumfries, in Prince William County, and had business interests there and in Georgetown, on the Maryland side of the Potomac River in present-day Washington, D.C.[18] In 1748, he sought a seat in the House of Burgesses; the process was controlled by more senior members of the court and he was not then successful, but he later emerged victorious in 1758.

Mason dealt with several local concerns, presenting a petition of Fairfax County planters against being assessed for a tobacco wharf at Alexandria, funds they felt should be raised through wharfage fees.

When word of passage of the Stamp Act reached Williamsburg, the House of Burgesses passed the Virginia Resolves, asserting that Virginians had the same rights as if they resided in Britain, and that they could only be taxed by themselves or their elected representatives.

[35] Mason drafted an act to allow for one of the most common court actions, replevin, to take place without the use of stamped paper, and sent it to George Washington, by then one of Fairfax County's burgesses, to gain passage.

Mason published a response in June 1766, satirizing the British position, "We have, with infinite Difficulty & Fatigue got you excused this one Time; do what your Papa and Mamma bid, & hasten to return your most grateful Acknowledgements for condescending to let you keep what is your own.

Word had just arrived of the passage of the Intolerable Acts, as Americans dubbed the legislative response to the Boston Tea Party, and a group of lawmakers including Lee, Henry, and Jefferson asked Mason to join them in formulating a course of action.

The Burgesses passed a resolution for a day of fasting and prayer to obtain divine intervention against "destruction of our Civil Rights", but the governor, Lord Dunmore, dissolved the legislature rather than accept it.

The 24 propositions that made up the Resolves protested loyalty to the British Crown but denied the right of Parliament to legislate for colonies that had been settled at private expense and which had received charters from the monarch.

With independence from Britain widely accepted as necessary among prominent Virginians,[5] the fifth convention, to meet in May 1776 at Williamsburg, would need to decide how Virginia would be administered henceforth, as the royal government was dead in all but name.

[49] That all men are born equally free and independent, and have certain inherent natural Rights, of which they cannot by any Compact, deprive or divest their Posterity; among which are the Enjoyment of Life and Liberty, with the Means of acquiring and possessing Property, and pursuing and obtaining Happiness and Safety.

On May 24, convention president Edmund Pendleton wrote to Jefferson about the committee's deliberations, "as Colo.[nel] Mason seems to have the ascendancy in the great work, I have Sanguine hopes it will be framed so as to Answer it's [sic] end, Prosperity to the Community and Security to Individuals".

Mason spoke repeatedly in the five days of debate, using oratory one hearer described as "neither flowing nor smooth, but his language was strong, his manner most impressive, and strengthened by a bit of biting cynicism when provocation made it seasonable".

[65] There was criticism of the constitution—Edmund Randolph later wrote that the document's faults indicated that even such a great mind as Mason's was not immune from "oversights and negligences": it did not have an amending process and granted two delegates to each county regardless of population.

[67] According to Henry C. Riely in his journal article on Mason, "The Virginia Constitution of 1776, whatever may have been the question raised long afterwards as to the contribution of other great leaders, stands, on the authority of Jefferson, Madison, and Randolph—to mention only the highest authority—as his creation.

[84] Although the Annapolis Convention saw only about a dozen delegates attend, representing only five states, it called for a meeting to be held in Philadelphia in May 1787 to devise amendments to the Articles of Confederation which would result in a more durable constitutional arrangement.

The committee met over the convention's July 4 recess and proposed what became known as the Great Compromise: a House of Representatives based on population, in which money bills must originate, and a Senate with equal representation for each state.

[99] According to Madison's notes, Mason urged the convention to adopt the compromise: However liable the Report [of the Grand Committee] might be to objections, he thought it preferable to an appeal to the world by the different sides, as had been talked of by some Gentlemen.

[101] Mason had failed to carry his proposals that senators must own property and not be in debt to the United States, but he successfully argued that the minimum age for service in Congress should be 25, telling the convention that younger men were too immature.

[111] Broadwater notes, "given the difficulty of the task he had set for himself, his stubborn independence, and his lack, by 1787, of any concern for his own political future, it is not surprising that he left Philadelphia at odds with the great majority of his fellow delegates".

[112] Madison recorded that Mason, believing that the convention had given his proposals short shrift in a hurry to complete its work, began his journey back to Virginia "in an exceeding ill humor".

Madison complained that Mason had gone beyond the reasons for opposing he had stated in convention, but Broadwater suggested the major difference was one of tone, since the written work dismissed as useless the constitution and the proposed federal government.

John Marshall, a future Chief Justice of the United States, downplayed the concern regarding the judiciary, but Mason would later be proved correct in the case of Chisholm v. Georgia (1793), which led to the passage of the Eleventh Amendment.

He resigned from the Fairfax County Court after an act passed by the new Congress required officeholders to take an oath to support the constitution, and in 1790 declined a seat in the Senate which had been left vacant by William Grayson's death, stating that his health would not permit him to serve, even if he had no other objection.

[133] Although Mason predicted that the amendments to be proposed to the states by the First Congress would be "Milk & Water Propositions", he displayed "much Satisfaction" at what became the Bill of Rights (ratified in 1791) and wrote that if his concerns about the federal courts and other matters were addressed, "I could cheerfully put my Hand & Heart to the new Government".

[152] Rutland, writing in 1961, asserted that in Mason's final days, "only the coalition [between New England and the Deep South at the Constitutional Convention] in Philadelphia that had bargained away any hope of eliminating slavery left a residue of disgust.

"[153] Catherine Drinker Bowen, in her widely read 1966 account of the Constitutional Convention, Miracle at Philadelphia, contended that Mason believed slaves to be citizens and was "a fervent abolitionist before the word was coined".

Mason fought on the side that failed, both at Philadelphia and Richmond, leaving him a loser in a history written by winners, even his speeches to the Constitutional Convention descend through the pen of Madison, a supporter of ratification.