Built in 1912, the African Queen did not achieve fame until 1951 when it played a starring role in the hit film of the same name. The vessel is currently located in Monroe County, Florida. (Arthur Lemon, Wisconsin Center for Film and Theater Research, 1951) The Baltimore-Washington Parkway in Anne Arundel and Prince George's counties, Maryland, was constructed between 1942 and 1954 as a component of a national parkway system. (Sara Amy Leach, April, 1988)

Some resources acquire historical qualities before the passage of 50 years because they either were not built to last that long, or, by their nature, are subject to circumstances that destroy their integrity before 50 years have elapsed. Such resources are viewed by scholars and by the public as "old" even before they are 50 years old. World War II frame temporary buildings were often constructed to meet temporary, intense demands for housing or office space and were not constructed to last long. While they tended to be viewed as automatically expendable, many in fact did survive for decades after the war. Mining structures in the Rocky Mountain West region have a short life-span both because the effects of weather and because entrepreneurs did not invest much in their construction in order to maximize gain and/or limit financial risks. Federal tax laws, competition within industry, changing transportation routes, and shifts in consumer tastes have jeopardized many early motel or motor court complexes, shopping centers, and other roadside buildings. Their rate of survival with integrity from the post-World War II era is very low. Many highways from that same era have undergone "improvements" that result in the loss of historic engineering qualities and original materials. The fact that a resource is jeopardized by a specific proposed project does not, in and of itself, render that resource more historically important than if it were not threatened. But one may evaluate whether a type or category of resources—as a whole—has faced loss at such a rate that relatively young survivors can be viewed as exceptional and historic.