Samuel Pumroy was the minister responsible for bringing the Newtown church into the Presbyterian fold. Pumroy was born on September 16, 1687 in Northampton, Massachusetts. After graduating from Yale College at age 18, he accepted a call to the Newtown church. Pumroy and his wife arrived in September 1708. In 1715, Pumroy applied for membership in the Presbytery of Philadelphia. On September 23, 1715, the Presbytery accepted Pumroy's application and gave a charter to the Newtown church, which then became the First Presbyterian Church of Newtown.

In 1724, Pumroy told the congregation that he needed help performing church duties. The members responded by appointing three members (Content Titus, James Renne, and Samuel Coe) to serve as ruling elders, thus forming the Newtown church's first Session. The Session tried to find out what had happened to members who had not attended church recently. The church later established a weekly Wednesday evening prayer and an autumn day of thanksgiving. The Newtown church began keeping records separate from town records. In 1727, Renne bought a book which was used to keep Session records. This book is the oldest document currently in FPCN's archives.

After serving as FPCN's pastor for 36 years, Pumroy died on June 30, 1744. His remains were moved twice: once from the town burial ground to the church cemetery, and again from the church cemetery to a common grave in Cypress Hills.