William Medill graduated from Newark Academy and was admitted to the bar in Delaware and Ohio. He served in the Ohio House of Representatives, including a stint as Speaker, and later in the United States House of Representatives. Medill held various public sector roles, such as the second assistant postmaster general and Commissioner of Indian Affairs, where he influenced Native American policies. He also presided over the Ohio Constitutional Convention and served as lieutenant governor and First Comptroller of the United States Treasury.

William Medill's political career reveals a blend of regional economic advocacy and federal fiscal stability, coupled with a complex approach to Indian affairs. His support for infrastructure development juxtaposes with his efforts to stabilize the financial system during his tenure as First Comptroller, suggesting a nuanced understanding of economic policy. Medill's role in the Ohio Constitutional Convention and his work on Native American relocation policies further illustrate a multifaceted approach to governance, balancing state interests with federal responsibilities.