When The Pennington School (then the Methodist Episcopal Male Seminary) opened its doors in 1838 in the small town of Pennington, New Jersey, the school was housed in one building and enrolled three students under the tutelage of one teacher. The New Jersey Conference of the Methodist Church, which founded the school, chose the site for its rural setting, which it believed conducive to health and learning. Early on, the founders identified three guiding principles: "the education of the physical, the training of the mental, and the grounding of the soul in character." Their principles reflected the vision of John Wesley, the founder of Methodism, who envisioned schools as places that cared for the whole individual; central to this philosophy was the belief that the real purpose of education is not just to fill students with information but to enable them to think.

Through the early years the School was blessed with a series of dedicated presidents and headmasters, as well as the support of the church. It steadily grew in enrollment with the addition of residence halls and classrooms to the main building, an administration building, Shaw Memorial Chapel, and a gymnasium and pool.

Originally founded as a college preparatory school for boys and young men, Pennington officially became a coeducational institution in the fall of 1854. The School was empowered by the New Jersey legislature to confer the degrees of Mistress of English Literature and Mistress of Liberal Arts upon young ladies who had finished their course of study. In March of 1910, it was announced that, with the coming fall, Pennington would again become a preparatory school for boys; it was not until 1972 that Pennington once again became a coeducational institution.

One of the School's most influential and beloved headmasters was Dr. Francis Harvey Green, who accepted the headmastership in 1920 and served for over 25 years. His well-remembered and oft-repeated advice to students to stimulate their intellectual curiosity was, "Look it up!" He was a friend to American literati like Robert Frost and Edwin Markham and hosted them in his campus home, Lowellden, now the Admission Office. He is remembered as an inspiring teacher and a dedicated leader through the difficult years of the Depression and Second World War, when tuition monies were scarce. He found funds and creative ways to continue Pennington's mission and welcomed students from all walks of life, including veterans returning from the war who needed to finish their educations.

By the late 1800s, international students were attracted to the School, introduced by businessmen with contacts in the United States and by Methodist missionaries in all parts of the world. Dozens of South Americans, Asians, and Europeans had their first introduction to America as students at The Pennington School and then went on to university education before returning home. Eventually, the School created its English as a Second Language program to formalize instruction for non-English speakers.

In 1973, in response to the recognition that there were bright and capable young people who did not have access to a traditional college preparatory program because they learned differently, the School took another innovative step by opening its Center for Learning, a college preparatory program for students with learning differences. Long before schools in general began to identify and serve this population, Pennington developed a small and selective program to prepare them for college and achieved a 100% success rate for admission.

In January of 1980, the School suffered a devastating blow when O'Hanlon Hall, built in 1901, burned to the ground. At the heart of the campus, this columned building housed administrative offices, classrooms, science labs, faculty residences, and the Shaw Memorial Chapel. In response to this disaster, Stainton Hall, a classroom and administration building named after Howard S. Stainton, was built in 1981; a new dormitory, Buck Hall, dedicated to alumnus Franklin Buck, was opened in 1982. In the summer of 1992, construction was completed on Corson House, the Headmaster's residence, and the Health Center was opened to patients in the fall of 1993. Autumn 2004 saw the completion of a Campus Center that is the centerpiece of the campus, housing a large student center and expanded and centralized facilities for the arts.

What remains permanent about Pennington is the attention we give our students, our acknowledgment that all deserve the best education we can provide, and the success that our students achieve both here and in life.