December 1952 (age 53)

On December 13, Sigurd attended a meeting of the Wisconsin Conservation Department to discuss management of the Flambeau River State Forest. Sigurd asked that a mile-wide strip of forest be preserved on each side of the Flambeau River. Several weeks later, the Department decided to fully protect a quarter-mile strip along each side of the river, and put in place very strict management of the remaining three-quarters of a mile. Some of the conservationists whom Sigurd represented were upset, but Sigurd was elated. He wrote to the director of the Wisconsin Conservation Department, Ernie Swift (famous in his own right as a conservationist), and said:

I am convinced...that the entire battle would have been lost if we had insisted on the original proposal. The strategy in my own mind was to get some sort of a commitment now, some definite policy laid down as to the wilderness core, no matter what its width happened to be at the moment. As I mentioned at Madison before the group, there comes a time in all of these efforts when proponents of a cause have to take what they can get and once having gotten a toe hold then lay plans for achieving part or all of the original objective. The important thing is to get the toe hold and if the Commission actually recognizes the wilderness concept with all that it implies, then that toe hold has been achieved.

December 1967 (age 68)

On December 1, Minnesota Gov. Harold LeVander gave his unqualified support to the establishment of Voyageurs National Park, one of Sigurd's major causes. His support meant that the state's leaders in both parties were committed to the park.

On December 10, acting on Sigurd's urging, Interior Secretary Stewart Udall announced his decision against building a new transmountain road through the heart of Great Smoky Mountains National Park.