John Mercer was a colonial

Colonialism

Colonialism is the establishment, maintenance, acquisition and expansion of colonies in one territory by people from another territory. It is a process whereby the metropole claims sovereignty over the colony and the social structure, government, and economics of the colony are changed by...

 American

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 lawyer

Lawyer

A lawyer, according to Black's Law Dictionary, is "a person learned in the law; as an attorney, counsel or solicitor; a person who is practicing law." Law is the system of rules of conduct established by the sovereign government of a society to correct wrongs, maintain the stability of political...

, land

Real property

In English Common Law, real property, real estate, realty, or immovable property is any subset of land that has been legally defined and the improvements to it made by human efforts: any buildings, machinery, wells, dams, ponds, mines, canals, roads, various property rights, and so forth...

 speculator, and author

Author

An author is broadly defined as "the person who originates or gives existence to anything" and that authorship determines responsibility for what is created. Narrowly defined, an author is the originator of any written work.-Legal significance:...

.

Born in Dublin, Ireland

Ireland

Ireland is an island to the northwest of continental Europe. It is the third-largest island in Europe and the twentieth-largest island on Earth...

, he came to Virginia

Virginia

The Commonwealth of Virginia , is a U.S. state on the Atlantic Coast of the Southern United States. Virginia is nicknamed the "Old Dominion" and sometimes the "Mother of Presidents" after the eight U.S. presidents born there...

 in 1720 where he built the colonial estate Marlborough (also called Marlboro; at Marlborough Point on the Potomac River

Potomac River

The Potomac River flows into the Chesapeake Bay, located along the mid-Atlantic coast of the United States. The river is approximately long, with a drainage area of about 14,700 square miles...

, in Stafford County

Stafford County, Virginia

Stafford County is a county located in the Commonwealth of Virginia, a U.S. state, and just across the Rappahannock River from the City of Fredericksburg. As of the 2000 census, the population was 92,446, increasing to 128,961 in 2010.. Its county seat is Stafford. In 2006, and again in 2009,...

). He was a leading Virginia attorney and lawyer to George Washington

George Washington

George Washington was the dominant military and political leader of the new United States of America from 1775 to 1799. He led the American victory over Great Britain in the American Revolutionary War as commander-in-chief of the Continental Army from 1775 to 1783, and presided over the writing of...

, as well as a colonial prosecutor for the King's court of Virginia.

He authored "Dinwiddianae" (4 November 1754-3 May 1757; also known as "The Dinwiddianae Poems and Prose"), "Abridgement of the Public Acts" (1737; also "An Exact Abridgment of the Public Acts of the Assembly of Virginia"), "First Code of Virginia
Laws" (1759), and "Abridgment of Virginia Laws" (“Mercer's Abridgement of the Laws of Virginia”). Mercer was also a founding member, secretary and general counsel of the Ohio Company of Virginia

Ohio Company

The Ohio Company, formally known as the Ohio Company of Virginia, was a land speculation company organized for the settlement by Virginians of the Ohio Country and to trade with the Indians there...

, a land speculating company that had George Washington as a member. His private library consisted of between 1500 and 1800 volumes. Did legal work for George Washington land deals as a down payment as a partner, died owing Washington the balance of partnership. His heirs deeded 790 acres (just west of the present day intersection of South Four Mile Run Drive and South Walter Reed Drive in Arlington County, Virginia) to Washington in payment.

Family

Married Catherine Mason (June 21, 1707-June 15, 1750) on June 10, 1725. Married again, after the death of his first wife, to Ann Roy (17??-1770), on November 10, 1750. He had several children (at least 11), many of which (5) died during childhood. Three sons lived to become prominent in Eighteenth Century America:

• George Mercer
  George Mercer (military officer)
  George Mercer was an American surveyor, military officer, and politician from Virginia....
  
   (1733-1784), surveyor, military officer, and politician from Virginia.

• James Mercer
  James Mercer (jurist)
  James Mercer , also known as William James Mercer, was born in Virginia at Malborough plantation on February 26, 1736. He was the son of John Mercer and Catherine Mason Mercer...
  
   (1736–1793), judge, lawyer, and jurist who served as a delegate for Virginia to the Continental Congress in 1779.

• John Francis Mercer
  John Francis Mercer
  John Francis Mercer was an American lawyer, planter, and politician from Virginia and Maryland. Born in 1759 in Marlborough, Stafford County, Virginia, to John Mercer and Ann Roy Mercer, he graduated from the College of William and Mary in 1775 and was a delegate for Virginia to the Continental...
  
   (1759–1821), Captain of the 3rd Virginia during the Revolutionary War
  American Revolutionary War
  The American Revolutionary War , the American War of Independence, or simply the Revolutionary War, began as a war between the Kingdom of Great Britain and thirteen British colonies in North America, and ended in a global war between several European great powers.The war was the result of the...
  
  , Anti-Federalist at the Constitutional Convention, and Governor of Maryland, 1801-03.

Uncle by marriage to George Mason

George Mason

George Mason IV was an American Patriot, statesman and a delegate from Virginia to the U.S. Constitutional Convention...

, became Mason's legal guardian, along with Mason's mother. Mason studied in Mercer's private library. The Mercer Library at the Prince William Campus of George Mason University

George Mason University

George Mason University is a public university based in unincorporated Fairfax County, Virginia, United States, south of and adjacent to the city of Fairfax. Additional campuses are located nearby in Arlington County, Prince William County, and Loudoun County...

 is named in his honor.

Grandfather of General George Mercer Brooke. Also grandfather of Charles Fenton Mercer (1778-1858; son of James).