John Dunlap was born in Tyrone, County Strabane, Ireland, in 1747. On February 4, 1773, Dunlap was married to Elizabeth Hayes Ellison.

In 1757, Dunlap was sent to Philadelphia as an apprentice to his uncle, printer-bookseller William Dunlap. In 1766, his uncle sold his stock of books and put his printing house in care of his nephew in order to pursue religious studies. Two years later, William Dunlap became an Anglican priest and took charge of the parish of Stratton in King and Queen County, Virginia, and sold his shop and equipment to John. John paid off his debt to his uncle in installments. Dr. Benjamin Rush, a close friend, reported that John was so poor he lived in his shop, sleeping on the floor under his counter.

John supported himself by printing sermons, handbills, and pamphlets. In 1771, Dunlap began publishing the weekly Pennsylvania Packet or The General Advertiser. By 1775, Dunlap's Packet was competing successfully. In 1776, Dunlap became an official printer to the government. As a result of this appointment, Dunlap became the first person to print the Declaration of Independence. However, Dunlap's Packet did not get the distinction of being the first publisher. On July 6, Benjamin Towne preempted Dunlap and published the Declaration of Independence in his newspaper, the Pennsylvania Evening Post.

By combining public pursuits with his printing business, Dunlap was able to establish a substantial fortune. An astute businessman, soldier (elected to the rank of first lieutenant in Philadelphia's historic Light Horse in 1781), politician, and speculator, Dunlap's determination and clout secured him fame as the founder of the nation's first successful daily newspaper. Despite his wealth and numerous accomplishments, his friend Dr. Rush revealed of Dunlap, "In his family he was less amiable and respectable than in society. Towards the close of his life he became intemperate so as to fall in the street."

Dunlap died of apoplexy on November 27, 1812.