As with other cultural resources survey work, reading a landscape requires a knowledge of the resource and the subject area. On-site surveys, documentary research, oral histories, and archeological investigations can reveal character-defining features, and provide evidence of a historic landscape’s visual, spatial, and contextual relationships. Preservation Brief No. 36 ("Preserving Cultural Landscapes," by Charles A. Birnbaum, US Department of the Interior, National Park Service, 1994) describes the process of reading a landscape.

A project’s Area of Potential Effects should be established to encompass the entire area that could be affected by the project, as reasonably envisioned. However, resources that extend beyond the designated APE might emerge during the survey, and in that case, survey responsibilities do not necessarily end at the original APE line. If any part of a historic landscape is located within a project APE, it has the potential to trigger a study of the entire resource, essentially expanding the APE to incorporate the whole property, just as when an APE encompasses part of an archeological site or some elements of a possible historic district.

The possibility of a historic landscape should be considered on some level on every survey, even when the possibility can be quickly dismissed, to see whether properties within the APE may constitute or be part of a historic landscape or district. Seek clues in patterns or groupings of resources or linkage to natural features. Remember that not all features need to be intact and that ruins or other physical remains can possess significance. Patterns of land use may be evident in multiples of features, such as rows, groupings, series, or clusters of the same or similar resources. They could include rows of trees used as windbreaks, a series of ponds and ditches, or groupings of farmsteads. Clues to survival of past landscapes can also be found in combinations of features that together create the sense of an earlier time, or in linkages among resources or with natural features. Knowledge of past building styles, technologies, and culture is essential for recognition of clues to historic landscapes. A landscape may be revealed by patterns and linkages among features, such as in the following examples:

• An agricultural area may feature tree-lined roads adjacent to fenced pastures and farmhouses, with each farmstead possessing features such as ponds, irrigation ditches, windmills, windrows, stone walls, barns, tankhouses, or silos, as well as less-obvious features such as woodlots or leased grazing lands.
• A mining landscape may display an above-ground concentration of stamp mills, headframes, building ruins, and scattered machinery, surrounded by large areas of pits and tailings; below-ground features such as tunnels, shafts, chambers, framing, and pumps, while not part of the visible landscape, would be included in the historic property.
• Logging properties may include scattered remains of logging activities, forests in various stages of reforestation, stumps with springboard holes, narrow-gauge railroad beds, rusted equipment, and logging camp sites.
• A series of buildings constructed in a style or organized in a pattern typical to an ethnic tradition may mark a landscape important for its association with a particular group.
• Traditional cultural practices centered on a topographic feature such as a sacred mountain could include surrounding ceremonial sites or related gathering areas.
• Industrial or agricultural activities are typically linked to roads, railroads, or bodies of water which were used to bring in supplies and take out products.
• Hydroelectric power generation systems generally include a series of interconnected features such as dams, penstocks, pumps, canals, power plants, and transmission lines.
• An irrigated agricultural colony is likely to be platted by its developer and organized for efficient delivery of water. It may include individual farmsteads; irrigation canals, pumps, and gates; field patterns; a road system; bridges over the canals; and irrigation-dependent crops.

Preliminary research conducted as the normal part of any cultural resources study may reveal the possibility of a previously unsuspected historic landscape. Traditional land use, historical associations, and ethnic associations can often be found in documentary research and oral histories, along with leads to further sources. Studies should be pursued as far as needed to reach a conclusion, but exhaustive speculative research is inappropriate. Preliminary research should generally include a review of both secondary sources and site-specific primary sources. If a visual survey and preliminary research fail to produce evidence of a potential historic landscape, no further effort in that direction is needed.

Evidence of potential landscapes might be found among sources such as those listed below. If a landscape is identified, further research among such sources should be conducted to develop historic context and evaluate the resource.

Written documents: Public records and published sources can reveal patterns of land use and historical associations. Property ownership and individuals can be traced in sources such as county assessor’s records, deeds, plat maps, historical atlases, city directories, court documents, voter registers, probate records, census records, military records, mining claims, local and county histories, cemetery records, published diaries, church records, tax records, water or mineral rights, and patent rights (homestead claims). Period publications like agricultural handbooks and periodicals can be sources for past field patterns and crop selection, while government agencies or universities may have comparative modern data that could help reveal agricultural land use patterns and changes. Libraries, museums, archives, historical or archeological societies, and universities may have local history files, early ethnographic records, academic research papers, newspapers, and manuscript collections. Librarians and archivists may be able to suggest additional local sources. The Internet offers growing access to published records and a key to unpublished documents in distant collections.

Graphic records: Aerial photos can reveal land-use patterns that are not obvious at ground level. Graphic evidence of historic land use can appear in topographic maps, assessors’ parcel maps, diseños, General Land Office maps, government reports, atlases, paintings, photographs, subdivision maps, as-built drawings, irrigation or reclamation district maps, Sanborn fire insurance maps, and other graphic records. Comparison of information in these records with existing land use may confirm whether current activities or traditions are a continuation of historic uses.

Oral history: Residents, cultural leaders, local historians, or traditional users returning for ceremonial, cultural, or gathering activities may be able to identify potential ethnographic landscapes that possess few visual or documentary clues.

The field survey and preliminary research should identify any resources requiring study within the APE, and determine whether or not they could constitute a potential historic landscape. If there is any landscape potential, or the reasonable appearance of such potential, a landscape study is likely to be needed. On the other hand, a finding that there is no potential for a historic landscape would conclude this aspect of the identification process.

No potential historic landscape present: If the survey and research have not disclosed any potential for a historic landscape within the project area, no further study will be necessary (although resources may still require evaluation as individual properties or a district). The finding of no potential landscape may be appropriate when there are no landscape elements present at all or when any elements are fragmentary, altered, or recent features lacking both significance and coherence. This finding should be used only when no landscape is present. It should not be used to find a landscape ineligible.

Include the following language or similar phrasing in summary statements and transmittal documents, giving reasons when appropriate:

• There appears to be no potential for a historic landscape within the APE [or Study Area] for this project. [For use when no potential landscape components are present.] Or,
• Intrusions [or alterations or loss of contributing elements] constitute a loss of integrity that eliminates any potential for a historic landscape. [For use when any landscape components are irretrievably and unmistakably compromised.] Or,
• The features within the APE possess no discernible potential for significance [or are substantially less than 50 years old] and have no potential to be contributing elements of a historic landscape. [For use when any possible landscape components demonstrably possess no potential for significance or coherence.]

Potential historic landscape present: If it appears that a potential historic landscape may be present within the APE, a landscape study should be undertaken when this approach best serves the resource’s values. Landscape studies should be developed to the extent needed to determine eligibility and justify conclusions, following the process outlined below. If a large or complex landscape is found, the project manager should be informed promptly so that alternative project designs to avoid the resource may be considered before an extensive evaluation is undertaken.

Before embarking on a major study, give due attention to a project’s potential for effect and a landscape’s likely boundary. Where a transportation facility is confined to a narrow corridor within a large unrelated landscape, a minor project within the right of way normally has little potential for effect. However, when the transportation facility is itself a historic property, when features within the right of way could be components of the potential landscape, or when important landscape components are immediately adjacent, even a relatively minor project might have potential to affect the landscape.