Which U.S. President, despite not being a lawyer, played a significant role in shaping American legal thought through his judicial appointments and writings on constitutional interpretation?

1. He was a prominent figure in the Whig party before its collapse.
2. His presidency was largely overshadowed by the looming Civil War.
3. He is often described as the 'last of the Founding Fathers' generation.
4. He appointed a pivotal Supreme Court Justice who would later have a major impact on legal precedent.