This article contributes to the intellectual and legal history of this constitutional document. It also provides a close study of how pre-constitutional laws are employed in writing constitutions. It examines the way Spanish colonial law, known as "derecho indiano" in Spanish, was used in the process of drafting the Constitution and particularly the way these constitutional activities and provisions related to the Americas. The article asserts that this pre-constitutional law was used in three distinct ways: as general knowledge related to the Americas and their institutions; as a source for providing a particular answer to a specific legal question; and in the debates about how grounded the Constitution is in historical sources and laws, its historicity. Although the example is drawn from Spanish colonial law and the Constitution of Cádiz, the general methodology will likely be appealing to others working in the fields of comparative constitutional law and constitutional history.