How does a property/district become historic?

Eligibility Criteria for Phoenix
The Phoenix Historic Preservation Commission shall evaluate each parcel of property within an area that is included in the application for a demonstrated quality of significance in local, regional, state, or national history, architecture, archaeology, engineering or culture, according to the following criteria:

Significance
Associated with the events that have made significant contribution to the broad patterns of our history; and/or
Associated with the lives of persons significant in our past; and/or
Embody the distinctive characteristics of a type, period or method of construction or that represent the work of a master or that possess high artistic values or that represent a significant and distinguishable entity whose components may lack individual distinction; and/or
Have yielded or may be likely to yield information important in the understanding of our pre-history or history of the city of Phoenix.
Age

Are at least 50 years old; or
Have acheived significance within the past 50 years if the property is of exceptional importance.
Integrity

Retain sufficient integrity of location, design, setting, materials, workmanship, feeling and association to convey their significance.


Consideration Factors for the Designation of Individual Structures
The following factors are considered in the designation of individual properties on the Phoenix Historic Property Register:

If the property is significant for its architectural, landscape, or aesthetic qualities, what are those qualities and why are they significant? Does the property retain enough of its significant design to convey these qualities? If not, how have additions or alterations contributed to or detracted from the significance of the resource?
If the property is significant for its association with historic events, what are the historically significant events or patterns of activity associated with the property? Does the existing building, object, or structure reflect in a tangible way the important historical associations? How have alterations or additions contributed to or detracted from the resource's ability to convey the feeling and association of the significant historical period?
If the property is significant because of its association with an individual, how long and when was the individual associated with the property during what period in his or her life? What were the individual's significant contributions during this period of association? Are there any other resources in the vicinity also having strong associations with the individual? If so, compare their significance and associations to that of the property being documented.
Does the property have an unusually important association with its location?
If the property is no longer at its original location, why did the move occur? How does the new location affect the historical and architectural integrity of the property?
How does the property compare with similar resources in the state, region or locality?
Consideration Factors for the Designation of Districts
The following factors are considered in designating architectural historic districts on the Phoenix Historic Property Register:
What are the features and characteristics that distinguish the district?
What are the origins and historical developments of the district? Are any architects, builders, designers or planners important to the district's development?
Does the district convey a sense of historic and architectural cohesiveness through its design, setting, materials, workmanship or association?
How do the architectural styles or elements within the district contribute to the feeling of time and place?
How have significant individuals or events contributed to the development of the district?
How has the district affected the historical development of the community, region or state? How does the district reflect the historical development of the community, region or state?
How have intrusions and non-contributing structures and buildings affected the district's ability to convey a sense of significance?
What are the qualities that distinguish the district from all its surroundings?