Robert E. Lewis began his career with a foundation in legal studies, attending Westminster College. He practiced law in Clinton, Missouri, and served as the prosecuting attorney for Henry County. Lewis transitioned into federal judicial roles, appointed by Presidents Theodore Roosevelt and Warren G. Harding. He held positions on the United States District Court for the District of Colorado, the Eighth Circuit, and the Tenth Circuit, demonstrating a long-standing commitment to judicial service. Lewis's career culminated in his assumption of senior status in 1940, reflecting his extensive experience and dedication to the judiciary.

Robert E. Lewis's career reveals a steadfast commitment to judicial integrity, underscored by his appointments from both Republican Presidents Theodore Roosevelt and Warren G. Harding. His long-term service in various federal courts suggests a dedication to stability and continuity in the judicial system. Notably, Lewis's career juxtaposes a traditional Republican alignment with a consistent focus on judicial roles, hinting at an underlying belief in the judiciary as a cornerstone of governance.