The Windsor Mill is on the National Register of Historic Places. Often questions are asked regarding the meaning of being on the register, and there is no one simple answer. First a property is nominated, and goes through a review process on the state level, then the National Park Service, the overseeing United States department for all historic sites on the register – the park service falls under the US Department of the Interior. If approved, the site is deemed to be a district, site, building, structure, or object of significance in American history and culture.
Besides the honor of the recognition, a site on the Historic Register is eligible for federal projects, licensing, and funding, as well as a 20% tax credit for income producing sites.
A full outline of the National Register of Historic Places program can be found at http://www.nps.gov/history/nr/regulations.htm
Regarding changes to the Windsor Mill, the property owner is allowed to make changes and upgrades to the property. For upcoming projects at the Mill, with the use of federal and state grants, a review process and approval must be made by The National Park Service.