Recently, we at Arizona Highways came across something interesting regarding an Arizona landmark. It's Roosevelt Dam, which forms Roosevelt Lake northeast of Phoenix.
Construction on the dam started in 1906 and was completed in 1911. In 1963, it was designated a National Historic Landmark by the National Park Service. But in 1999, it lost that designation. In fact, it's one of only 35 such landmarks in the U.S., and the only one in Arizona, to have its "historic" designation withdrawn. That's out of about 2,500 landmarks nationwide.
Why did this happen? Well, the National Historic Landmarks Program lists a few criteria for removing the designation. In some cases, a property will be designated, and then additional information will be uncovered that suggests the designation is unwarranted. In other cases, errors are made in the process and must be rectified. But these situations are uncommon.
What happened to Roosevelt Dam, though, was that it ceased to meet the requirements for "historic" status. Or, in the Park Service's words:
The property has ceased to meet criteria for designation; the qualities for which it was originally designated have been lost or destroyed.
Roosevelt Dam's original structure was 280 feet high and contained 344,000 cubic yards of masonry. It was a staggering feat of engineering that originally was expected to take two years, but instead lasted five. But as the dam got older, concerns about safety began to take hold. Engineers determined that during a "maximum flood event," the dam would be unable to safely release water to prevent flooding. And if a sizable earthquake were to occur near the dam, it could have failed entirely. For those downstream from Roosevelt Lake, the consequences would have been catastrophic.
From 1989 to 1996, a new concrete-block structure was built around the original dam, raising its height to 357 feet and increasing Roosevelt Lake's storage capacity by about 300,000 acre-feet. But in doing so, the qualities of the original dam were no longer apparent. As the Park Service puts it: "After modifications, the dam no longer retained integrity of design, materials, workmanship, feeling, or association."
Accordingly, Roosevelt Dam's National Historic Landmark designation was withdrawn in 1999. That said, it's still a fascinating structure and an engineering marvel in its own right. You can get an excellent view of the dam and the lake from Roosevelt Lake Bridge, which was completed during the renovation so traffic wouldn't have to go over the dam.
The National Park Service, Salt River Project and the U.S. Bureau of Reclamation each have histories of Roosevelt Dam if you'd like to learn more.