George, the son of Joseph Junkin, was the sixth of fourteen children born in Cumberland County, Pennsylvania. His early years were spent on his father's farm where he prepared for college. He graduated from Jefferson College (now Washington and Jefferson College) in 1813. After studying theology privately, he entered the Theological Seminary of the Associate Reformed Presbyterian Church, in New York City and was licensed to preach by the Presbytery of Monongahela in 1816. He was soon called to the charge of the United Congregations of Milton, Pennsylvania and McEwensville, Pennsylvania, where he remained for about eleven years. He left the reformed denomination to become a Presbyterian in 1822. In 1830, he became Principal of the Manual Labor Academy, at Germantown, Pennsylvania, one of the first institutions of the kind to go into operation in the United States. Two years later he became the first President of Lafayette College. In 1841, he accepted the Presidency of Miami University in Oxford, Ohio remaining three years, when he again returned to Easton. He was Moderator of the General Assembly in 1844.