ColonelStevens Thomson Mason (December 29, 1760 – May 10, 1803) was an American lawyer, military officer and planter who served in theContinental Army during theRevolutionary War. Mason was also a delegate in theVirginia General Assembly and aRepublicanU.S. Senator from 1794 to 1803.^[1][2]

Mason was born toThomson Mason (1733–1785);^[1][2] and his wife atChopawamsic inStafford County, Virginia.^[1] His ancestors had emigrated generations earlier and owned thousands of acres of land (some developed and farmed by enslaved labor) in Maryland and Virginia. His maternal great grandfather was an attorney and significant landowner in Maryland, and (his grandmother) Ann Eilbeck Mason was his only heir, and determined to provide for her younger sons (including Thomson Mason) by securing land and slaves. His uncleGeorge Mason IV had inherited the Mason family estates byprimogeniture in 1735 (though then underage, he took control upon reaching legal majority). His grandmother invested in real estate being developed along thePotomac River inLoudoun County, which by the time of her death may have exceeded the lands his uncle inherited by primogeniture. After education by private tutors as a boy, he and his brothers also had access to the library of his lawyer uncleJohn Mercer nearFredericksburg. Stevens T. Mason then traveled toWilliamsburg, Virginia for higher education at theCollege of William & Mary, concentrating in legal studies.

Admitted to the Virginiabar, Mason began a private legal practice inDumfries, Virginia inPrince William County. His uncleGeorge Mason was one of his clients until his death in 1792.^[3] Especially after his father's 1785 death at the family'sRaspberry Plain plantation in what had becomeLoudoun County, Mason operated farms using enslaved labor, as would his descendants. In the 1787 Virginia tax census, Stevens T. Mason owned 33 slaves over 16 years of age, as well as 38 slaves under age 18, 28 horses, 76 cattle, 4 wheeled vehicles and a stud horse.^[4]

During theAmerican Revolutionary War, as his uncle George served in the Virginia General Assembly and drafted theVirginia Declaration of Rights as well as the first Virginia constitution and state seal, Stevens Mason served as an officer in the Continental Army and in the Virginia militia. By theBattle of Yorktown, he was a brigadier general in the Virginia militia as well as an aide to GeneralGeorge Washington.

Following the war, Loudoun County voters elected him as one of their (part-time) representatives in the Virginia State House of Delegates in 1783, and he served alongside veteran John Carter, although neither won re-election the following year.^[5] In 1787 he won election to the Virginia State Senate representing Loudoun and nearby Fauquier Counties (thus serving in 4 General Assembly sessions), but failed to win re-election in 1791, being replaced by veteran politician Francis Peyton.^[6] Meanwhile Stevens Thomson Mason also won election (alongside Levin Powell) as Loudoun County's delegate to the Virginia Ratification Convention in 1788,^[7] during which his uncle (one of Stafford County's representatives) unsuccessfully fought against ratification, but ultimately caused Virginia's congressional delegates to propose theBill of Rights modeled on his Virginia Declaration of Rights and which was later approved by Congress and the states as a series of ten Constitutional amendments. Less than two years following his uncle's death, in 1794, Loudoun County voters returned Stevens Thomson Mason to the Virginia House of Delegates.^[8] Fellow legislators elected him to theUnited States Senate to fill the vacancy caused by the resignation ofJames Monroe. Stevens Thomson Mason won re-election in 1797 and again in 1803, and thus served from 18 November 1794, until his death inPhiladelphia, Pennsylvania.^[9]

While in the Senate Mason handed a copy of the secretJay Treaty toPierre Adét, French minister to the United States. The senator along withSenator Pierce Butler leaked the document to the American press.^[10] Since his country was at war withGreat Britain and hated the idea of a treaty of “amity” between it and the United States, Adét gave the document toBenjamin Bache, publisher of The Aurora — a newspaper — with the hope of raising just the sort of public outcry that ensued—and even, perhaps, of blocking ratification of the treaty.

Mason was the only senator to vote against the confirmation ofOliver Ellsworth as the chief justice of the Supreme Court.^[11]

He is interred in the family burying ground atRaspberry Plain inLoudoun County, Virginia.

Mason married Mary Elizabeth Armistead on May 1, 1783.^[1][2] The couple had six children:^[1]

• John Thomson Mason (January 8, 1787 – April 17, 1850)^[1]
• Armistead Thomson Mason (1787 – February 6, 1819)^[1]
• Stevens Thomson Mason (1789 – 17 November 1815)^[1]
• Mary Thomson Mason (1791–1813)^[1]
• Emily Rutger Mason (1793–1837)^[1]
• Catherine Mason (born 1795)^[1]

Brother ofJohn Thomson Mason (1765–1824);^[1][2] half-brother ofWilliam Temple Thomson Mason (1782–1862);^[1][2] first cousin ofGeorge Mason V (1753–1796);^[1][2] first cousin once removed ofThomson Francis Mason (1785–1838),George Mason VI (1786–1834),Richard Barnes Mason (1797–1850), andJames Murray Mason (1798–1871);^[1][2] father ofArmistead Thomson Mason (1787–1819) andJohn Thomson Mason (1787–1850);^[1][2] uncle ofJohn Thomson Mason Jr. (1815–1873);^[1][2] and grandfather ofStevens Thomson Mason (1811–1843), first governor of Michigan.^[1][2] His great granddaughterKate Mason Rowland would be one of the founding members of theDaughters of the Confederacy and also write a two-volume biography ofGeorge Mason IV.

• List of members of the United States Congress who died in office (1790–1899)

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• Democratic-Republican Party United States senators from Virginia
• Mason family
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