James Smith was born in Dublin, Ireland, sometime between 1713 and 1720. His choice to conceal the date he was born remains a mystery, although it was not in Smith's nature to be furtive. He and his father, a respectable farmer, immigrated to Lancaster in 1727. Throughout his life, he pursued classical studies and attended the Philadelphia Academy, which is now known as the University of Pennsylvania. He studied the art of land surveying, which proved to be an important role for that particular time period. In Lancaster, he took up studying law in Thomas Cookson's office. After he was admitted into the Pennsylvania Bar in 1745, he began his practice in Shippensburg. Smith's office was then moved to the more populated city of York. Smith continued practicing law for the remainder of his life. He also made his mark in the iron-making business when he opened his own iron-making business on Codorus Creek in 1771.

Upon being selected as the delegate to the provisional conference in Philadelphia, Smith he asserted, "If the British administration should determine by force to effect a submission to the late arbitrary acts of the British parliament, in such a situation, we hold it our indispensable duty to resist such force, and at every hazard to defend the rights and liberties of America." He then became the delegate to the state convention in 1775. Smith organized the Pennsylvania Militia and took on the role of captain, although his later election as Colonel was out of respect more than for the attainment of power. His involvement in the Continental Congress from 1776 to 1778 earned him a seat as a member of the State House of Representatives in 1780. Prior to this, he was a signer of the Declaration of Independence and therefore a founding father. This endeavor was clearly the pinnacle moment of Smith's life. Smith was not only a signer, but he also was rumored to have had involvement with the drafting as well.

After becoming Brigadier General for the state militia and state counselor, he returned to York to continue his law practice. Shortly before Smith's death, most of his work was destroyed in an office fire, making it nearly impossible to find his plans for future endeavors. Many referred to Smith as a cheerful man who was known for his humor. James Smith died on July 11, 1806. His body was buried in the First Presbyterian Church of York. The monument over his grave states that he died in the ninety-third year of his life. It is speculated that his real age at the time of his death was much younger.