A local historic district is a set of "resources" (buildings and landscapes) that has been given legal protection against inappropriate physical changes, with a local historic preservation ordinance passed to outline the district, establish a Commission to oversee it, and implement the relevant State and Federal laws. Typically, within a historic district, any physical change to the exterior of a resource must receive preliminary approval by the local Historic District Commission (HDC), a municipal board composed of architects, contractors, and historic district residents, and at-large members, certifying that the proposed change is appropriate under the United States Secretary of the Interior's Standards for Rehabilitation, and any other guidelines laid out in the State and local ordinances.
Properties within a historic district are, however, eligible for Historic Rehabilitation Tax Credits: renovations made to the standards of the HDC and SHPO may receive State and Federal tax credits worth up to 45% of the cost of the renovations.
How to start a historic district
The process of creating a historic district involves creation of a Study Committee by the City Council or County Commission. The Study Committee examines the structures and landscape in a particular area to determine whether the area has historic significance. Generally, an area must be characterized by structures that are at least 50 years old (meaning that mid-Century ranches and other Modernist homes are now becoming eligible for preservation), that have some significance to the architectural, historical, or cultural background of the area.
If the Study Commission determines that the area in question does have historic significance, it may recommend the creation of a historic district, which would then have to be created by ordinance by the City Council or County Commission. Often, this final decision can be contentious, with some property owners in the district opposed to adding another layer of regulation on their properties.
My house is in a district, but it's not "historic"
Sometimes, historic districts are misunderstood as protecting big, fancy, iconic houses - sure, that massive Victorian mansion down the street is "historic", but my house is just a house! "Pretty house protection" is only a small part of preservation, though, with the iconic houses providing only a piece of the district's significance. All resources in a district, big or small, new or old, are typically considered to be part of the overall historic landscape.
The true architectural and cultural significance of a historic district is made up by the collection of resources as a whole, and their relationship to one another: the modest workers' homes on the side streets behind the grand avenues just as important a piece of the district, from a historical perspective, as are the newer contributions. A new house built in a historic district typically becomes a part of the district, and subject to the same rules as other resources, because the district is as concerned with the overall pattern and relationship of buildings as it is with individual buildings on their own.