In the year 1750, McKean finally finished his studies with Dr. Alison, and shortly thereafter moved in with his uncle, John Finney, who was a wealthy lawyer at the time.

Shortly after the death of Mary Borden, at some point, McKean reconnected with Sarah Armitage, who he'd marry on September 16, 1774, and would live at the northeast corner of Third and Pine Streets in Philidelphia.

The minority Country Party was largely Irish Presbyterian (also referred to as "Scotch-Irish" in America), was centered in New Castle County, and quickly advocated independence from the British.

The revolutionary slogan "no taxation without representation" had originated in the north of Ireland under the British Penal Laws, which denied Presbyterians and Catholics the right to vote for members of the parliament.

[4] As such, he generally worked in partnership with Caesar Rodney from Kent County and in opposition to his friend and neighbor, George Read.

McKean then disputed his use of the word "conscience" so loudly and so long that a challenge was given by Ruggles and accepted in the presence of the Congress.

A few days after McKean cast his vote, he left Congress to serve as colonel in command of the Fourth Battalion of the Pennsylvania Associators, a militia unit created by Benjamin Franklin in 1747.

[7] In a conservative reaction against the advocates of American independence, the 1776-1777 Delaware General Assembly did not reelect either McKean or Rodney to the Continental Congress in October 1776.

However, the British occupation after the Battle of Brandywine swung opinions enough that McKean was returned to Congress in October 1777 by the 1777–1778 Delaware General Assembly.

When poor health caused Samuel Huntington to resign as president of Congress in July 1781, McKean was elected as his successor.

The position was mostly ceremonial with no real authority, but the office required McKean to handle a good deal of correspondence and sign official documents.

Upon hearing of it, McKean made the long ride to Dover, Delaware, from Philadelphia in a single day, went to a room in an inn, and that night, virtually by himself, drafted the document.

As a result, the state capital, New Castle, was unsafe as a meeting place, and the Sussex County seat, Lewes, was sufficiently disrupted by Loyalists that it was unable to hold a valid general election that autumn.

As president, McKean was primarily occupied with recruitment of the militia and with keeping some semblance of civic order in the portions of the state still under his control.

"[10] Some weeks later, Mckean and General William Irvine wrote to Pennsylvania Governor Thomas Mifflin and discussed the mission of federal committees to negotiate with the Rebels, describing them as "well disposed."

However, in seeking a third term in 1805, McKean was at odds with factions of his own Democratic-Republican Party, and the Pennsylvania General Assembly instead nominated Speaker Simon Snyder for governor.

The governor's beliefs in stronger executive and judicial powers were bitterly denounced by the influential Aurora newspaper publisher William P. Duane and the Philadelphia populist Michael Leib.

After they led public attacks calling for his impeachment, McKean filed a partially successful libel suit against Duane in 1805.

[13] Some of McKean's other accomplishments included expanding free education for all and, at age eighty, leading a Philadelphia citizens group to organize a strong defense during the War of 1812.

He spent his retirement in Philadelphia in writing, discussing political affairs, and enjoying the considerable wealth that he had earned through investments and real estate.

With University of Pennsylvania law professor James Wilson (Founding Father), McKean published "Commentaries on the Constitution of the United States" in 1790.

McKean was over six feet tall, and he typically wore a large cocked hat and carried a gold-headed cane.

[17][18] In the 1969 Broadway musical, 1776, McKean is portrayed as a gun-toting cantankerous old Scot who cannot get along with the wealthy and conservative planter George Read.

[citation needed] McKean was portrayed by Bruce MacKay[19] in the original Broadway cast and Ray Middleton in the 1972 film version.

McKean served as state president only temporarily, filling the vacancy created by John McKinly's capture and resignation and awaiting the arrival of George Read.

A joint ballot of the Pennsylvania General Assembly and the council chose the president from among the twelve counsellors for a one-year term.

The chief justice of the Pennsylvania Supreme Court was also selected by the General Assembly and Council for the life of the person appointed.