Final answer:
Mt. Harvard has the lowest elevation at 4,395.6 meters when compared to Mt. Elbert, Mt. Whitney, and Denali.
Step-by-step explanation:
The mountain with the lowest elevation among those listed (Mt. Elbert, Mt. Whitney, Mt. Harvard, and Denali) is Mt. Harvard, with an elevation of 4,395.6 meters. This can be determined by comparing the elevations: Mt. Elbert (4,401.2 meters), Mt. Whitney (4,421 meters), Mt. Harvard (4,395.6 meters), and Denali (6,190.5 meters). Thus, Mt. Harvard has the lowest elevation compared to the other mountains mentioned.