In the law regulating historic districts in the United States, a contributing property or contributing resource is any building, object, or structure which adds to the historical integrity or architectural qualities that make the historic district, listed locally or federally, significant. Government agencies, at the state, national, and local level in the United States, have differing definitions of what constitutes a contributing property but there are common characteristics. Local laws often regulate the changes that can be made to contributing structures within designated historic districts. The first local ordinances dealing with the alteration of buildings within historic districts was in Charleston, South Carolina in 1931.
Properties within a historic district fall into one of two types of property: contributing and non-contributing. A contributing property, such as a 19th Century mansion, helps make a historic district historic, while a non-contributing property, such as a modern medical clinic, does not. The contributing properties are key to a historic district's historic associations, historic architectural qualities, or archaeological qualities. A property can change from contributing to non-contributing and vice versa if significant alterations take place.
According to the National Park Service, the first instance of law dealing with contributing properties in local historic districts occurred in 1931 when the city of Charleston, South Carolina, enacted an ordinance that designated the "Old and Historic District." The ordinance declared that buildings in the district could not have changes made to their architectural features visible from the street. By the mid-1930s, other U.S. cities followed Charleston's lead. An amendment to the Louisiana Constitution led to the 1937 creation of the Vieux Carre Commission, which was charged with protecting and preserving the French Quarter in the city of New Orleans. The city then passed a local ordinance that set standards regulating changes within the quarter. Other sources, such as the Columbia Law Review in 1963, indicate differing dates for the preservation ordinances in both Charleston and New Orleans. The Columbia Law Review gave dates of 1925 for the New Orleans laws and 1924 for Charleston. The same publication claimed that these two cities were the only cities with historic district zoning until Alexandria, Virginia adopted an ordinance in 1946. The National Park Service appears to refute this.