[1] William Jessup left his native home, Long Island, in early adulthood to study at Yale College, graduating in 1815.

In 1838 Jessup became the presiding judge of the Eleventh Judicial District of Pennsylvania, in which capacity he rode circuit from 1838 until 1851.

Upon arrival, he was selected to chair the platform committee to write the party's statement of political principles.

In November 1860, the Republican ticket of Abraham Lincoln and Hannibal Hamlin was elected to lead the new national administration, and soon thereafter, the Civil War broke out.

[1] In 1861, the Commonwealth of Pennsylvania appointed Jessup to serve as a liaison with the White House, naming him as their emissary to a high-level conference in early 1861 on how to implement Lincoln's call for the enlistment of 75,000 members of the Northern state militias into the new Federal army.