The political theology of Rev. John Witherspoon (1723-1794) had a profound impact on the development of ideas on religion and government during the Founding Period as a prominent educator, clergyman, and signatory of the Declaration of Independence. This paper uncovers the far-reaching impact of Witherspoon's political theology during America's struggle for independence. Witherspoon shaped the views on religious liberty of his prominent students and colleagues including James Madison and Benjamin Rush. Witherspoon's understanding of religious liberty was shaped by his view that the government should encourage popular piety through moral education while avoiding sectarian religious establishments.