Duffy's Marsh, located in Marquette, Wisconsin, is a privately-owned earth dam completed in 1997 with a primary purpose of recreation. This beautiful marsh area is situated along an unnamed tributary to the Grand River and covers a surface area of 1302 acres, with a drainage area of 6.82 square miles. The dam stands at a height of 8 feet and has a structural height of 8 feet, providing storage capacity of 5750 acre-feet.

With a low hazard potential and a fair condition assessment, Duffy's Marsh is a popular destination for water resource and climate enthusiasts looking to explore and enjoy the natural surroundings. Despite being privately owned, the dam is state-regulated and subject to inspections, ensuring safety measures are in place for visitors and the surrounding environment. The marsh offers a serene setting for recreational activities, attracting visitors to its tranquil waters and diverse wildlife.

In 2004, the dam underwent modifications, further enhancing its recreational offerings and maintaining its structural integrity. With a designated inspection frequency of 10 years, Duffy's Marsh continues to provide a safe and enjoyable environment for visitors to appreciate the beauty of Wisconsin's natural landscapes. Whether for birdwatching, fishing, or simply taking in the scenic views, Duffy's Marsh is a must-visit destination for those passionate about water resources and climate conservation.