Here's some information from the National Park Service website on how to get your building on the National Register of Historic Places:
"The National Register nomination process usually starts with your State Historic Preservation Office*(SHPO). Contact your SHPO or check their web page for National Register information, research materials, and necessary forms to begin the nomination process. If the property is on federal or tribal land, then the process starts with the Federal Preservation Office or Tribal Preservation Office.
To be considered eligible, a property must meet the National Register Criteria for Evaluation. This involves examining the property’s age, integrity, and significance.
• Age and Integrity. Is the property old enough to be considered historic (generally at least 50 years old) and does it still look much the way it did in the past?
• Significance. Is the property associated with events, activities, or developments that were important in the past? With the lives of people who were important in the past? With significant architectural history, landscape history, or engineering achievements? Does it have the potential to yield information through archeological investigation about our past?
• Nominations can be submitted to your SHPO from property owners, historical societies, preservation organizations, governmental agencies, and other individuals or groups. Official National Register Nomination Forms are downloadable or from your State Historic Preservation Office. National Register Bulletins can also provide guidance on how to document and evaluate certain types of properties. Sample Nominations provide additional useful information.
• The SHPO notifies affected property owners and local governments and solicits public comment. If the owner (or a majority of owners for a district nomination) objects, the property cannot be listed but may be forwarded to the National Park Service for a Determination of Eligibility (DOE).
• Proposed nominations are reviewed by your state’s historic preservation office and the state’s National Register Review Board. The length of the state process varies but will take a minimum of 90 days.
• Complete nominations, with certifying recommendations, are submitted by the state to the National Park Service in Washington, D.C. for final review and listing by the Keeper of the National Register of Historic Places. The National park Service makes a listing decision within 45 days.
*Note: National Register nominations of Tribal properties start with the Tribal Historic Preservation Officer. National Register nominations of federal properties start with the agency’s Federal Preservation Officer."