Williamson H. Dilg (1869-1927) was the driving force behind the establishment of the Upper Mississippi River Wildlife and Fish Refuge from north of Winona, Minnesota to Rock Island, Illinois. He was one of the most prominent voices for conservation and the environment in the 1920's and was the founder and first president of the Izaak Walton League. Dilg crossed the country speaking, writing, and organizing to preserve 240,000 acres of upper Mississippi River bottomland and backwaters and prevent them from being diked and drained. On June 7, 1924, just two and a half years after the first Izaak Walton League meeting, the U.S. Congress authorized the Refuge. This was the first time in U.S. history that the federal government purchased large tracts of private lands for conservation and public use, and 2024 marks the centennial anniversary of its establishment.

Dilg and the League then moved on to other issues such as protecting the elk in Jackson Hole, Wyoming, strengthening migratory bird laws, and protecting the Superior National Forest from exploitation by timber interests. Dilg was referred to as "a man of dauntless courage, persuasive eloquence, and inspiring zeal in the protection of fish and fishing" by others, and spent most of the remaining eleven months of his life in Washington, D.C. lobbying Congress and the Coolidge administration to establish a cabinet level "Department of Conservation." The League he founded had grown to over 2,850 chapters and over 200,000 members.

He died at age 58, and newspapers all over the nation noted his passing.