National Register GIS Map Update

In March 2024, the National Register team made a major update to the National Register layer on the THC GIS viewer, which can be accessed at https://tnmap.tn.gov/historicalcommission/. The viewer is an online map that shows the location of historic properties listed in the National Register of Historic Places (shown by a pink triangle and/or polygon) and properties that have been recorded in the Historic Resource Survey (shown by a yellow circle). The update includes exact boundaries for 90% of Tennessee’s 2,200+ National Register listed properties, including all residential and commercial historic districts. Knowing the exact boundaries is important for understanding which resources are included in the listing and therefore may be eligible for funding programs or consideration in federal planning processes. Determining the physical extent of a listing used to be a multistep process, but the Viewer update has turned that into a one step process of searching by address or zooming into a particular area. Clicking on a National Register pink triangle or polygon triggers a pop-up box containing basic information about the listing and a link to related documentation.

The process to map National Register listings began around 2019 in partnership with the Fullerton Laboratory for Spatial Technology at Middle Tennessee State University. The first National Register layer, published in July 2022, had a triangle for every listing and exact boundaries for 32% of the listings. In the Fall of 2022, National Register staff assumed full responsibility for maintaining and updating the layer. The ongoing boundary mapping process involves interpreting National Register documentation and plotting the boundaries while ensuring as much accuracy as possible. Along the way, National Register staff have corrected errors in nominations and are working to clarify the boundaries of properties listed in the 1970s before federal regulations required exact boundaries. As of May 2024, staff have corrected or clarified more than 100 nominations. The boundary clarification project is a unique initiative among State Historic Preservation Offices, and the National Park Service has recognized its importance by touting the THC’s project as a model for other states to follow.