Lewis is a privately owned dam located in Polk, Wisconsin, along the Knapp Creek. Built in 1931, this Earth dam serves primarily for recreational purposes, with a normal storage capacity of 130 acre-feet and a maximum discharge of 757 cubic feet per second. The dam stands at a height of 16 feet and spans 50 feet in length, providing a surface area of 35 acres for activities such as fishing and boating.

Managed by the Wisconsin Department of Natural Resources (WIDNR), Lewis Dam has a low hazard potential and is considered to be in fair condition as of the last assessment in May 2020. Despite its age, the dam has undergone modifications in 1955 to ensure its structural integrity. With ongoing state regulation, inspection, and enforcement in place, Lewis Dam continues to be a safe and enjoyable recreation spot for visitors.

While the dam poses a low risk in terms of potential hazards, its location within a very high-risk area (Risk Assessment Level 1) highlights the importance of consistent monitoring and maintenance. The dam's controlled spillway, along with its fair condition assessment and regular inspection schedule, contribute to the overall safety of the structure. As an essential part of the local water resource infrastructure, Lewis Dam remains a vital asset for the community and a popular destination for water resource and climate enthusiasts.