What is the National Register of Historic Places?Updated
The National Register of Historic Places is the official listing of buildings, sites, and objects significant in American history and culture.
The National Register is managed in each state by the State Historic Preservation Office (SHPO). The National Trust does not manage the National Register!
Generally, to be listed on the Register, a barn would have to be 50 years old and outstanding architecturally, have associations with an important person in history or be part of a farm complex that has several extant historic buildings. Each state handles the Register differently, so I encourage you to check with your SHPO to see if your barn might qualify.
Listing on the Register is an honorary designation which does not carry any restrictions on what you can do with your property (you can even tear it down if you want). However, if you take advantage of any public funds (grants, tax credits, etc); you may have to agree to certain restrictions (these vary from program to program).