Wetlands don’t often get second chances, but Horicon Marsh in Wisconsin did. The Wisconsin Department of Natural Resources describes its history as a change from wetland to wasteland and back again. The marsh now covers about 32,000 acres, and huge flocks of geese stop there each fall. It was the result of decades of work by people determined to restore the land.
How a thriving marsh almost disappeared
The marsh basin took shape when glaciers from the last Ice Age gave rise to it. The DNR says people have lived near it for a very long time, with nomadic hunters arriving as early as 12,000 years ago. The changes began in 1846 when the town of Horicon built a dam to power a sawmill. The water rose nine feet, and the marsh became Lake Horicon, which people of the time considered the largest man-made lake in the world. After 23 years of operation, disputes led to the removal of the dam, and the marsh slowly became a refuge for wildlife again.
The next wave of damage came from hunting and farming. Unregulated hunting devastated the duck populations from the 1870s to the early 1900s. Then, many people saw little value in the marsh. Private landowners dug ditches to drain their land for farming, and the local sentiment changed to favor draining the whole marsh. A main ditch dug between 1910 and 1914 served that purpose. Those farming experiments failed. The peat soil was exposed, dried, and caught fire, and the marsh was abandoned.
The fight to bring it back
In 1921, conservation-minded people launched a fight to restore the marsh. A breakthrough came in 1927, when the state legislature passed the Horicon Marsh Wildlife Refuge Bill. The bill called for land purchases and a dam at Horicon to bring back the marsh’s water levels, the DNR said.
But the work didn’t end there. In the 1940s, the U.S. Fish and Wildlife Service acquired the upper end of the marsh and made it a National Wildlife Refuge. Today, about one-third of the marsh is managed by the state and about two-thirds by the federal government. Together they form one of the largest freshwater marshes in the United States. The DNR says that set the marsh on the road to recovery.
Geese, crops and the work ahead
The marsh is also known for its geese, which come there in the autumn. A 1983 conference paper provides a sense of how big the flocks can get. The author, Richard A. Hunt of the Wisconsin DNR, said the refuge’s fall Canada goose population was about 200,000 at its peak when he presented an earlier paper in 1973. Since then, he said, changes in the Horicon area had reduced the peak to fewer than 100,000. So the numbers are not set in stone, and they can change with time. More recently, the U.S. Fish and Wildlife Service’s 2025 fall surveys of the refuge counted anywhere from about 800 to more than 18,000 Canada geese per survey.
The paper also discusses the more painful side of that success. Damage to crops around the refuge by geese has been a chronic problem, Hunt wrote. The paper also outlines a new way of paying for that damage. It’s a reminder that a comeback can bring new challenges for the marsh’s neighbors.
The DNR says the marsh is still under pressure today. It says the biggest impacts come from the surrounding uplands, where intensive agriculture and suburban development have led to excess sediment and runoff entering the marsh. Protecting a wetland also means protecting the land around it. Not all damage is permanent, as Horicon shows, but it takes steady effort to return to health.