In order for a site to gain designation from the National Park Service, it has to “possess nationally significant natural, cultural, or recreational resources”; “be a suitable and feasible addition to the National Park System”; and “require direct NPS management instead of protection by some other government agency or by the private sector” [PDF]. The NPS has to conduct a thorough study to see if a place meets those criteria, and Congress gives the final yea or nay.
All in all, it’s a pretty involved process. But just because a site achieves National Historic Landmark Designation doesn’t mean it gets to keep it forever. To date, about three dozen landmarks have lost their status. Most of them simply “ceased to meet criteria for designation,” which often happens because the landmark itself ceased to exist. Several burned down accidentally, including the Kate Chopin House in Louisiana and Maine's Wickyup estate, which was home to aviator and polar explorer Richard E. Byrd.
Others were intentionally demolished by their owners, which may come as a surprise to anyone who assumed that National Historic Landmark Designation protects a place from intentional destruction: It doesn’t. The house in downtown Altoona, Pennsylvania, where chemist Charles B. Dudley lived in later life, is a good example of how this can happen. Its owner during the 1970s and 1980s didn’t maintain it well, and the house was significantly dilapidated by the time a new owner took over in the 1990s. Unfortunately, that person wanted to use the plot for hospital parking and managed to resist local efforts to preserve the landmark. It was razed in 1999.
Sometimes, extensive remodeling can unintentionally strip a property of its defining historical features. Chicago’s Grant Park Stadium (better known as Soldier Field) lost its designation in 2006 after undergoing renovations to make it a more modern NFL stadium. Since its Doric columns and other design elements are now overshadowed by the bowl, the stadium is no longer considered historically significant.
Any property that secured designation before December 13, 1980, can only lose its status because it ceased to meet the original criteria. More recently designated landmarks can also be withdrawn because of a “prejudicial procedural error” or “professional error” that occurred during the designation process, or because new information “demonstrates that the property does not possess sufficient significance.” In short, the NPS reserves the right to admit mistakes and also change its mind as our national values evolve.