I. DEFINING BOUNDARIES FOR NATIONAL REGISTER PROPERTIES

The preparer of a National Register nomination collects, evaluates, and presents the information required to document the property and justify its historical significance. Among the decisions the preparer must make is the selection of the property's boundaries: in addition to establishing the significance and integrity of a property, the physical location and extent of the property are defined as part of the documentation. Boundary information is recorded in Section 10, Geographical Data, on the National Register Registration Form. This bulletin is designed to assist the preparer in selecting, defining, and documenting boundaries for National Register properties. The bulletin addresses the factors to consider and includes examples that illustrate properly defined boundaries for a variety of property types.

WHY BOUNDARIES ARE IMPORTANT

Carefully defined boundaries are important for several reasons. The boundaries encompass the resources that contribute to the property's significance. Boundaries may also have legal and management implications. For example, only the area within the boundaries may be considered part of the property for the purposes of Federal preservation tax incentives and charitable contributions. State and local laws that require consideration of historic resources may also refer to boundaries in the application of implementing regulations or design controls. National Register boundaries, therefore, have legal implications that can affect the property's future. Under Federal law, however, these considerations apply only to government actions affecting the property; National Register listing does not limit the private owner's use of the property. Private property owners can do anything they wish with their property, provided no Federal license, permit, or funding is involved.

Under Section 106 of the National Historic Preservation Act of 1966, as amended, Federal agencies must take into account the effect of their actions on historic properties (defined as properties in, or eligible for, the National Register of Historic Places) and give the Advisory Council on Historic Preservation the opportunity to comment. To be in compliance with the act, Federal agencies must identify and evaluate National Register eligibility of properties within the area of potential effect and evaluate the effect of the undertaking on eligible properties.

The area of potential effect is defined as the area in which eligible properties may be affected by the undertaking, including direct effects (such as destruction of the property) and indirect effects (such as visual, audible, and atmospheric changes which affect the character and setting of the property). The area of potential effect may include historic properties that are well beyond the limits of the undertaking. For example, a Federal undertaking outside of the defined boundaries of a rural traditional cultural property or an urban historic district can have visual, economic, traffic, and social effects on the setting, feeling, and association of the eligible resources.

Large properties present special problems. For example, an undertaking in a narrow corridor, such as a pipeline, may affect part of a large archeological site, traditional cultural property, or rural historic district. Such properties may extend far beyond the area of potential effect or access may be denied in areas beyond the undertaking. It is always best to consider the entire eligible property, but it may not be possible or practical to define the full extent of the property. In such cases, reasonable, predicted, estimated, or partial boundaries encompassing resources within the area of potential effect may be the only way to set the limits of contributing resources when the entire property cannot be observed or evaluated from historic maps or other documents (as in the case of subsurface archeological resources). Consider all available information and select boundaries on the basis of the best information available. When defining boundaries of large resources extending beyond the area of potential effect, it is advisable to consult the State historic preservation office.

GETTING HELP

In addition to the guidance in this bulletin, assistance is also available from State Historic Preservation Officers, Federal Preservation Officers, and the staff of the National Register of Historic Places. These professionals can help preparers with general questions and special problems. For assistance with specific questions or for information on how to contact the appropriate State Historic Preservation Officer or Federal Preservation Officer, contact the National Register of Historic Places, National Register, History and Education, National Park Service, 1849 C Street, NW, Washington, D.C. 20240.

Several other National Register publications are also available to assist preparers. National Register Bulletin: How to Complete the National Register Registration Form provides the basic instructions for boundary selection and documentation. The following instructions, which are consistent with those in How to Complete the National Register Registration Form, provide additional assistance for the preparer. The following discussion addresses many property types by considering the special boundary problems associated with each type and providing case studies to assist the preparer in dealing with such issues. Bulletins that deal with specific property types may also be useful (see the list of National Register Bulletins at the end of this publication).

DECIDING WHAT TO INCLUDE

Selection of boundaries is a judgment based on the nature of the property's significance, integrity, and physical setting. Begin to consider boundaries during the research and data-collection portion of the nomination process. By addressing boundary issues during the field and archival research, the preparer can take into account all the factors that should be considered in selecting boundaries. When significance has been evaluated, reassess the boundaries to ensure appropriate correspondence between the factors that contribute to the property's significance and the physical extent of the property.

Select boundaries that define the limits of the eligible resources. Such resources usually include the immediate surroundings and encompass the appropriate setting. However, exclude additional, peripheral areas that do not directly contribute to the property's significance as buffer or as open space to separate the property from surrounding areas. Areas that have lost integrity because of changes in cultural features or setting should be excluded when they are at the periphery of the eligible resources. When such areas are small and surrounded by eligible resources, they may not be excluded, but are included as noncontributing resources of the property. That is, do not select boundaries which exclude a small noncontributing island surrounded by contributing resources; simply identify the noncontributing resources and include them within the boundaries of the property.

Districts may include noncontributing resources, such as altered buildings or buildings constructed before or after the period of significance. In situations where historically associated resources were geographically separated from each other during the period of significance or are separated by intervening development and are now separated by large areas lacking eligible resources, a discontiguous district may be defined. The boundaries of the discontiguous district define two or more geographically separate areas that include associated eligible resources.

FACTORS TO CONSIDER

There are several factors to consider in selecting and defining the boundaries of a National Register property. Compare the historic extent of the property with the existing eligible resources and consider integrity, setting and landscape features, use, and research value.

• Integrity: The majority of the property must retain integrity of location, design, setting, feeling, and association to be eligible. The essential qualities that contribute to an eligible property's significance must be preserved. Activities that often compromise integrity include new construction or alterations to the resource or its setting. Natural processes that alter or destroy portions of the resource or its setting, such as fire, flooding, erosion, or disintegration of the historic fabric, may compromise integrity. For example, an abandoned farmhouse that has been exposed to the elements through years of neglect may have lost its integrity as a building; however, it may retain integrity as an archeological site.
  
• Setting and Landscape Features: Consider the setting and historically important landscape features. Natural features of the landscape may be included when they are located within the district or were used for purposes related to the historical significance of the property. Areas at the margins of the eligible resources may be included only when such areas were historically an integral part of the property. For example, a district composed of farmsteads along a creek may include the creek if it runs through the district, if the creek was important in the original siting of the farmsteads, or if the creek was a source of water power or natural resources exploited by the farmsteads. Consult National Register Bulletin: Guidelines for Evaluating and Documenting Rural Historic Landscapes for additional guidance in selecting boundaries for rural historic landscapes.
  
• Use: Consider the historic use of the property when selecting the boundary. The eligible resource may include open spaces, natural land forms, designed landscapes, or natural resources that were integral to the property's historic use. Modern use may be different, and some modern uses alter the setting or affect built resources. The effect of such uses must be assessed in identifying resources that retain integrity. For example, a Hopewell mound archeological site now used as a golf course may retain integrity where the form of the prehistoric earthworks has been preserved, but construction of sand traps or other landscaping that altered landforms would compromise integrity. A marsh that provides plant materials for traditional basketmakers may retain integrity where it remains in its natural wetland condition, but may have lost integrity where it has been drained and cultivated.
  
• Research Potential: For properties eligible under Criterion D, define boundaries that include all of the resources with integrity that have the potential to yield important information about the past. Such information is defined in terms of research questions to which the information pertains, and the property should include the com-ponents, features, buildings, or structures that include the information. For example, an eligible prehistoric longhouse site should include longhouse features as well as associated pit features, middens, and hearths. Geographically separate but historically associated activity areas may also be included in the property even when they are not adjacent to the main concentration of eligible resources. For example, lithic procurement and processing loci that were historically associated with a village site but geographically separated from it may be included in a discon-tiguous district. Remember that many properties eligible under other criteria include contributing archeological resources that may yield important information about the property. Consider the extent of associated archeological resources when selecting boundaries.
  

SELECTING BOUNDARIES

Identify appropriate natural or cultural features that bound the eligible resource. Consider historical and cartographic documentation and subsurface testing results (for archeological resources) in addition to existing conditions. Some boundaries can be directly observed by examining the property; others must be identified on the basis of research. Take into account the modern legal boundaries, historic boundaries (identified in tax maps, deeds, or plats), natural features, cultural features, and the distribution of resources as determined by survey and testing for subsurface resources.

Owner objections may affect the listing of the entire property, but not the identification of the boundaries. If the sole private owner of a property or the majority of the private owners (for properties with multiple owners) objects to listing, the property (with boundaries based on an objective assessment of the full extent of the significant resources) may be determined eligible for the National Register but not listed.

Boundaries should include surrounding land that contributes to the significance of the resources by functioning as the setting. This setting is an integral part of the eligible property and should be identified when boundaries are selected. For example, do not limit the property to the footprint of the building, but include its yard or grounds; consider the extent of all positive subsurface test units as well as the landform that includes the archeological site; and include the portion of the reef on which the vessel foundered as well as the shipwreck itself.

• Distribution of Resources: Use the extent of above-ground resources and surrounding setting to define the boundaries of the property. For archeological resources, consider the extent of above-ground resources as well as the distribution of subsurface remains identified through testing when defining the boundaries of the property.
  
• Current Legal Boundaries: Use the legal boundaries of a property as recorded in the current tax map or plat accompanying the deed when these boundaries encompass the eligible resource and are consistent with its historical significance and remaining integrity.
  
• Historic Boundaries: Use the boundaries shown on historic plats or land-ownership maps (such as fire insurance or real estate maps) when the limits of the eligible resource do not correspond with current legal parcels.
  
• Natural Features: Use a natural feature, such as a shoreline, terrace edge, treeline, or erosional scar, which corresponds with the limit of the eligible resource.
  
• Cultural Features: Use a cultural feature, such a stone wall, hedgerow, roadway, or curb line, that is associated with the significance of the property, or use an area of modern development or disturbance that represents the limit of the eligible resource.
  

Selecting boundaries for some properties may be more complicated, however. Consider and use as many features or sources as necessary to define the limits of the eligible resource. In many cases, a combination of features may be most appropriate. For example, the National Register boundaries of a property could be defined by a road on the south, a fence line on the west, the limits of subsurface resources on the north, and an area of development disturbance on the east. Consider map features or reasonable limits when obvious boundaries are not appropriate.

• Cartographic Features: Use large-scale topographic features, contour lines, or section lines on United States Geographical Survey maps to define the boundaries of large sites or districts.
  
• Reasonable Limits: Use reasonable limits in areas undefined by natural or cultural features. For example, define the boundary of a property as 15 feet or 5 meters from the edge of the known resources, or define a straight line connecting two other boundary features. If a surveyed topographic map is available, select a contour line that encompasses the eligible resources. Reasonable limits may also be appropriate for a rural property when there is no obvious house lot or natural or cultural feature to use. Be sure that an appropriate setting is included within arbitrary boundaries, however, and explain how the limits were selected.
  

REVISING BOUNDARIES

Boundaries for listed properties need to be revised when there are changes in the condition of the resources or the setting. If resources or setting lose integrity and no longer contribute to the significance of the property, it is appropriate to revise the boundaries. Revisions may also be appropriate for nominations prepared in the early years of the National Register program, when nominations had limited or vague boundary documentation. Follow the guidance presented in this bulletin when revising boundary documentation.