Over the next few years, more rangers were hired and the park kennels were expanded. Each ranger was assigned a team of seven dogs and a district of the park that they had to patrol in the winter. Ranger Grant Pearson, who was hired by Karstens in 1926, recalls being told that he was lacking in experience but considered capable of learning. To test him, Karstens said, "I'll send you on a patrol trip alone. You will be gone a week. If you don't get back by then I'll come looking for you, and you had better have plans made for a new job."
Patrols lasted months at a time; in between, rangers would return to Headquarters, restock provisions, and head out once again. With the assistance of the dogs, who pulled the supply-loaded sleds and hauled logs, these pioneer rangers also constructed cabins along the boundaries to provide shelter for them and their dogs while they were out on patrol. By the late 1920s, the kennels were thriving, and in 1929, the present kennel building was constructed. By 1936, fifty dogs and fourteen pups were housed and cared for at the National Park Service (NPS) kennels, and they soon became one of the most popular summertime attractions for the increasing numbers of tourists who were finding their way to the park. Over the course of the next three decades, a series of legislative acts led to a renaissance of interest in the sled dogs and strengthened NPS commitment to their presence in the park.
In 1980, another incentive for using sled dogs at the park was provided with the passage of the Alaska National Interest Lands Conservation Act. This legislation tripled the size of Mount McKinley National Park, changed its name to Denali National Park and Preserve, and designated the original two-million acre park parcel as wilderness under the 1964 Wilderness Act. According to this act, wilderness is "an area where the earth and its community of life are untrammeled by man, where man himself is a visitor who does not remain." This new legal designation of wilderness prohibited certain activities, such as the use of motorized equipment and mechanized transport. Travel by sled dogs provided the perfect alternative; the dogs allowed the rangers to continue carrying out the park's mission during the winter months.
Today, Denali's dogs continue to provide transportation for rangers during the winter months and aid the park's most popular interpretive program during the summer. Each year, an average of 3,000 patrol miles are logged throughout the park's interior, all on the back of sleds pulled by NPS huskies. During the summer, attendance at the daily sled demonstrations totals over 50,000 annually. The highlight for visitors comes when five dogs are hitched to a wheeled sled and a naturalist takes the dogs for short runs on a gravel track around the kennels. However, it is in the wintertime that Denali's sled dogs prove, with each day of eager service, that they are the heart of a tradition and the true symbol of the Denali wilderness.