Most of the cabins in our tract are historic and many are interested in becoming an historic district according to a designation in the National Register of Historic Places.  What are the pros and cons of getting listed as a "district"?  Would this offer protection from the Forest Service as far as removal of cabins or reducing the number of structures?

I think it's wonderful that you are considering becoming an historic "district" under the National Register of Historic Places designation. A few point to keep in mind: Not all the cabins in the tract or vicinity need to be included. Some may opt out, and that is fine. There is always strength in numbers when dealing with the Forest Service or government agencies, such as the county. And yes such a designation would inhibit the FS from removing or reducing structures. I strongly urge you to contact your State Historical Preservation Office (SHPO) for advice on how to proceed and ask them to recommend a consultant with experience in Historic districts for you to work with..