At What Cost To Preserve Everything of Historic Value...

The National Register of Historic Places (NRHP) is the United States federal government's official list of districts, sites, buildings, structures, and objects deemed worthy of preservation. A property listed in the National Register, or located within a National Register Historic District, may qualify for tax incentives derived from the total value of expenses incurred preserving the property.
The passage of the National Historic Preservation Act (NHPA) in 1966 established the National Register and the process for adding properties to it. Of the more than one million properties on the National Register, 80,000 are listed individually. The remainder are contributing resources within historic districts. Each year approximately 30,000 properties are added to the National Register as part of districts or by individual listings.
For most of its history the National Register has been administered by the National Park Service (NPS), an agency within the United States Department of the Interior. Its goals are to help property owners and interest groups, such as the National Trust for Historic Preservation, coordinate, identify, and protect historic sites in the United States. While National Register listings are mostly symbolic, their recognition of significance provides some financial incentive to owners of listed properties. Protection of the property is not guaranteed. During the nomination process, the property is evaluated in terms of the four criteria for inclusion on the National Register of Historic Places. The application of those criteria has been the subject of criticism by academics of history and preservation, as well as the public and politicians.

Budget

See also: United States federal budget and United States budget process
As of 2016, the National Park Service has an annual budget of about $3 billion and an estimated $12 billion maintenance backlog.
The National Park Services budget is divided into two primary areas, discretionary and mandatory spending. Within each of these areas, there are numerous specific purposes to which Congress directs the services activities. The budget of the National Park Service includes discretionary spending which is broken out into two portions: the direct operations of the National Parks and the special initiatives. Listed separately are the special initiatives of the service for the year specified in the legislation.
For Fiscal Year 2010, the service has been charged with five initiatives.
They include: Stewardship and Education; Professional Excellence; Youth Programs; Climate Impacts; and Budget Restructure and Realignment
https://en.wikipedia.org/wiki/National_Register_of_Historic_Places

When the money's tight, some jobs don't get done — and those jobs start to pile up. Today, the total backlog of needed maintenance at U.S. national parks is $11.9 billion. That backlog includes $500 million in needed repairs at Yosemite National Park, $100 million of which is considered critical. Grand Canyon National Park needs $330 million, due largely to outstanding wastewater and water system upgrades. The Blue Ridge Parkway, which saw a record 15 million visitors last year, needs $478 million to help address the wear and tear from all of those drivers.

Most of Arizona's state parks are managed by a private company called Recreation Resource Management. Tallgrass Prairie National Preserve in Kansas is owned by the National Park Service but jointly managed and funded by The Nature Conservancy. Still, Fretwell says she knows that people are uncomfortable with the idea of a private company running the national parks. She hears it from her own friends: It's going to turn into Disneyland. They're going to charge us $1,000 a day.
http://www.npr.org/2016/03/08/466461595/national-parks-have-a-long-to-do-list-but-cant-cover-the-repair-costs