Properties eligible for Rock Island Landmark designation include buildings, districts, sites and other noteworthy structures that are at least 50 years old. Structures designated can include high style mansions or the humblest barn if one of the following criteria is met:
Significant value as part of the heritage of the nation, state or community.
Associated with an important person or event in national, state or local history.
Representative of an architectural and/or landscape type, which exemplifies a period, style, craftsmanship, method of construction or use of local materials, and retains a high degree of integrity.
Notable work of a master builder, designer, architect or artist.
Identifiable as a familiar visual feature in the community, owing to its unique location or physical characteristics.
Its character as a particularly fine or unique example of a utilitarian structure such as a barn, gas station, or other commercial structure with a high level of integrity or architectural significance.
Areas that have yielded or are likely to yield information important to history or prehistory.