It's shameful that the National Park Service forces its sled dogs to live on chains. Chaining dogs is cruel. That's why jurisdictions across the United States have banned or severly restricted the practice.

Maybe the previous commenter could be more explicit about how she would like to see the lives of the Denali sled dogs changed?

I have not been to the kennels, but her comment led me to look into (via the web) how the Denali sled dogs are kept, and they seem to have pretty rich lives with lots of human contact and stimulation. In the winter, they spend a lot of time on patrol with rangers in the backcountry. In the summer, they meet hundreds of visitors each day, who are encouraged to pat and love on the dogs to their hearts content. It's true that many of the dogs are chained, but this allows visitors to interact freely with them as they wander from dog to dog. At the end of the day, the dogs go for strolls with park volunteers:

"In the long summer evenings, volunteers take the dogs for “walks,”
during which the powerful huskies drag their companions down the edge of
the park road. This popular volunteer program not only provides the
dogs with exercise and a chance to get away from the kennels, but also
forges special bonds between the dogs and their walkers, bonds that
sometimes last for years."

When the dogs are retired, they are adopted out to suitable homes. As an indication of what the park considers a suitable home, here is a quote from the adoption application:
"We look for people who lead an active, outdoors-y life. Though these dogs are “retiring” they still have a TON of energy and need large amounts of regular exercise. We need to know that you can provide that for a sled dog and then bring them in to sleep on a nice soft couch at the end of the day."

(There is a nice picture of a retired sled dog reclining on the couch with her adopters too.)
 
Source: http://www.nps.gov/dena/planyourvisit/kennels.htm
 
I am not disagreeing that chaining a dog 24/7 is inhumane, but it's not clear to me that the Denali dogs are leading impoverished lives at all. My dogs, who snooze on the couch at home while I go off to work each day, would probably be happy to change their sometimes boring existence for that of a Denali sled dog.
 
This is a what it looks like to be a chained-up Denali dog during the summer (scroll down a bit): http://suzmca.blogspot.com/2010/08/alaska-3-of-6-denali-our-furry-friend...

I have visited the sled dogs in Denali a couple times (May & Aug, seperate years).  Yes, they were on chains - very long chains.  And they seemed happy & healthy to me - & I have issues with people cooping dogs up in houses, so 'chaining' them, I agree, sounds really cruel.  Which is why I'm thankful to the person ("Ranger") who replied after doing some research...  These dogs aren't pets, they work for a living, and they are treated with love and respect by the people who's lives depend on them.