districts are identified by surveying historic resources and delineating appropriate boundaries that comply with all aspects of due process. Depending on local ordinance or State law, property owners permission may be required; however all owners are to be notified and given a chance to share their opinion. Most local historic districts are constricted by design guidelines that control changes to the properties included in the district. Many local commissions adopt specific guidelines for the "tout ensemble" of each neighborhood, although some smaller commissions rely on the Secretary of Interior Standards. For most minor changes, homeowners can consult with local preservation staff at the municipal office and receive guidance on and permission for the changes. Major changes however, require homeowners to apply for a Certificate of Appropriateness (COA), and the changes may be decided upon by the historic commission or architectural review board. The COA process is carried out with all aspects of due process, with formal notification, hearings, and fair and informed decision making. According to the National Park Service, historic districts are one of the oldest forms of protection for historic properties. The city of Charleston, South Carolina is credited with beginning the modern day historic districts movement. In 1931 Charleston enacted an ordinance which designated an "Old and Historic District" administered by a Board of Architectural Review. Charleston's early ordinance reflected the strong protection that local historic districts often enjoy under local law. It asserted that no alteration could be made to any architectural features which could be viewed by the public from the street. Local historic districts, as in New Orleans and Savannah, Georgia, predate the Register by 10 years or more as well. Local historic districts are most likely to generate resistance because of the restrictions they tend to place on property owners. Local laws can cause residents "to comply with (local historic district) ordinances." The issue of local historic districts and the impact on property values is a concern to many homeowners. The effects have been extensively studied using multiple methodologies including before-and-after analysis and evaluating comparable neighborhoods with and without local designation status. Recent factual analysis has been conducted by independent researchers in a number of states, including New Jersey, Texas, Indiana, Georgia, Colorado, Maryland, North and South Carolina, Kentucky, Virginia, and elsewhere. As stated by economist Donovan Rypkema, "the results of these studies are remarkably consistent: property values in local historic districts appreciate