Lewis is a privately owned earth dam located in Big Horn, Wyoming, along Gypsum Creek offstream. Built in 1948 for irrigation purposes, the dam stands at 19 feet high and spans 1540 feet in length. With a storage capacity of 122 acre-feet, Lewis has a spillway width of 40 feet and an uncontrolled spillway type.

Despite its low hazard potential, Lewis is currently in poor condition as of the last inspection in May 2017. The dam is regulated by the Wyoming State Engineer's Office and undergoes regular inspections, with an inspection frequency of 5 years. While the risk assessment for Lewis indicates a moderate level of risk, there are no specific risk management measures or emergency action plans in place.

As a vital water resource structure in the region, Lewis serves as a reminder of the importance of maintaining and monitoring dams for the safety of surrounding communities and the sustainability of water resources in the face of changing climate conditions.