In developing the historic context for the landscape, a geographic area, theme, and period of significance should be established. Comparison with other properties will generally take place within that area, theme, and period. In other words, if an agricultural landscape is evaluated in the context of citrus growing in Riverside County from 1880 to 1920, it should be compared to other citrus growing areas in that geographic area from the same period.

The data base of historic landscapes is still fairly small, but an effort should be made to develop a comparative context for evaluation. Historical research or a windshield survey of similar areas can be adequate to establish a basis for comparison in some cases, or the National Park Service may have related case studies that could be useful. Some sense of the historic context must be found; no property can be adequately evaluated in a vacuum.

When other resources have been identified within the same context, consider how this resource compares with them. Compare significance, integrity, and essential physical features of properties related by common historic contexts. For example, a landscape that is the most significant, most intact, only remaining, earliest, best example, or a good example of the property type is more likely to be eligible than one that is altered, less significant, commonplace, or a poor example. Documentation should include a statement describing the qualities of the resource in comparison with any others against which it has been measured. Comparison statements need not be detailed, but they must be accurate and defensible, supportable by evidence if challenged.