Editor's note: As part of National Parks Traveler's Centennial Series, a collection of papers and essays commemorating the National Park Service Centennial, Dr. Harry Butowsky, a National Park Service historian who oversaw the agency's digital library, put together the following list of key events and legislation from the first century of the National Park Service. In retirement, Dr. Butowsky has built a more powerful digital library of National Park Service history and natural resource materials at npshistory.com.

Yellowstone National Park Act, 1872 - The Act signed into law on March 1, 1872, established the world's first true national park. It withdrew more than two million acres of the public domain in the Montana and Wyoming territories from settlement, occupancy, or sale to be "dedicated and set apart as a public park or pleasuring-ground for the benefit and enjoyment of the people." It placed the park under the control of the Secretary of the Interior and gave the Secretary responsibility for preserving all timber, mineral deposits, geologic wonders, and other resources within the park. The establishment of the park set a precedent for placing other natural reserves under federal jurisdiction.

Antiquities Act of 1906 - The Antiquities Act, signed by President Theodore Roosevelt on June 8, 1906, grew out of a movement to protect the prehistoric cliff dwellings, pueblo ruins and early missions in the Southwest. It authorized Presidents to proclaim and reserve "historic landmarks, historic and prehistoric structures, and other objects of historic or scientific interest" on lands owned or controlled by the United States as "national monuments." It also prohibited the excavation or appropriation of antiquities on federal lands without permission from the department having jurisdiction. Nearly a quarter of the units currently in the National Park System originated in whole or part from the Antiquities Act.

Act to Establish the National Park Service, 1916 (Organic Act) - By August 1916 the Department of Interior oversaw 14 national parks, 21 national monuments, and the Hot Springs and Casa Grande Ruin reservations, but there was no unified leadership or organization to operate them. Lacking this, the parks and monuments were vulnerable to competing interests. With encouragement from future directors Stephen T. Mather and Horace Albright, the National Geographic Society, journalists, railroad interests and others, Congress passed what is often known as the Organic Act, which established the National Park Service and placed all the existing parks under its management. The legislation established the basis for the fundamental mission, philosophy, and policies of the National Park Service.

Reorganization of 1933 - A major reorganization within President Franklin Roosevelt's executive branch in 1933 had a tremendous impact on the National Park Service. Specifically, two executive orders, effective August 10, 1933, transferred the War Department's parks and monuments to the National Park Service. In addition the National Park Service received all the national monuments held by the Forest Service and the responsibility for virtually all monuments created thereafter. It also assumed responsibility for the parks in the nation's capital, which had previously been managed by a separate office in Washington. The reorganization was one of the most significant events in the evolution of the National Park System. The Service's holdings were greatly expanded and there was now a single, national system of parklands. With the 1933 reorganization and new responsibilities for historical areas, historic preservation became a primary mission of the National Park Service.

Preservation of Historic Sites Act, 1935 - The Historic Sites Act grew out of the National Park Service's desire for a stronger legal underpinning for its expanding historical programs and from recognition outside the Service of the need for greater federal assistance to historic properties. The Act declared "a national policy to preserve for public use historic sites, buildings and objects of national significance for the inspiration and benefit of the people of the United States." It assigned broad powers and duties to the Secretary of the Interior and the Service, to include conducting surveys of historic properties to determine which possess exceptional value as commemorating or illustrating U.S. history. They were authorized to conduct research; to restore, preserve, and maintain historic properties directly or through cooperative agreements with other parties; and to mark properties, establish and maintain related museums, and engage in other interpretive activities for public education. The legislation's provision for a historic site survey proved valuable in identifying potential additions to the National Park System.

Mission 66, 1956-1966 - Mission 66 was a 10-year program, initiated by National Park Service Director Conrad L. Wirth in 1956, to upgrade facilities, staffing, and resource management throughout the System by the 50th anniversary of the Service in 1966. Congress appropriated more than a billion dollars over the 10-year period for Mission 66 improvements. The legacy of the program included dozens of visitor centers, hundreds of employee residences, as well as the Mather and Albright employee training centers at Harpers Ferry and the Grand Canyon.

Wilderness Act of 1964 - In the Wilderness Act of 1964, Congress adopted a policy of securing wilderness areas for the benefit of present and future generations of Americans. It established a National Wilderness Preservation System, to be composed of federally owned areas designated by Congress as "wilderness areas," that would be administered in a way that would leave them unimpaired for the use and enjoyment of the American people as wilderness areas. The legislation prompted the Service to carefully examine all park land that potentially qualified as wilderness areas and provided additional legal protection for park areas threatened with development.

Land and Water Conservation Fund Act of 1965 - The Land and Water Conservation Fund Act established a fund for acquiring new recreation lands either within or adjacent to existing park units or new parks. Money for the fund would come from surplus property sales, motorboat fuel taxes, and other sources. A portion of the money in the fund would come from fees charged at existing parks. The fund was administered by the Bureau of Outdoor Recreation, a new Interior bureau established in 1962. The legislation took away the Park Service's responsibilities for recreation planning and assistance together with some of its staff and fund, but the Service later regained these functions when the Bureau, reconstituted in 1978 as the Heritage Conservation and Recreation Service, expired in 1981.

National Historic Preservation Act of 1966 - The 1966 Act required that all historical parks be entered in the National Register of Historic Places. National Park Service and other federal agency measures that would affect historic sites became subject to review by state historic preservation officers and the Advisory Council on Historic Preservation, a new federal agency established by the Act.

Wild and Scenic Rivers Act, 1968 - The Wild and Scenic Rivers Act provided for the protection and preservation in free-flowing condition of selected rivers that possessed outstanding scenic, recreational, geologic, fish and wildlife, historic, or cultural values. It identified eight rivers and adjacent lands in nine states as initial components of the wild and scenic rivers system, to be administered variously by the secretaries of Agriculture and the Interior. It also named 27 other rivers or river segments to be studied as potential additions to the wild and scenic rivers system. The legislation added to the National Park System long, winding units with complex management challenges.

National Trails System Act, 1968 - The National Trails System Act provided for the establishment of both national recreation trails accessible to urban areas, to be designated by the Secretary of the Interior and the Secretary of Agriculture according to specified criteria; and national scenic trails to be established by Congress. It designated two national scenic trails as initial components of the trails system: the Appalachian Trail and the Pacific Crest Trail. It also ordered 14 others routes to be studied for possible national scenic trail designation. Along with the Wild and Scenic Rivers Act, this legislation expanded the diversity of units in the National Park System.

Volunteers in the Parks Act of 1969 - This legislation authorized the Secretary of the Interior to establish a "volunteers in the parks" program to aid in interpretation functions or other visitor services or activities in and related to areas administered by the National Park Service. The legislation provided a vehicle that allowed the Service to utilize volunteer help and services. The number of volunteers and volunteers has consistently grown and has proven increasingly beneficial. National Environmental Policy Act of 1969 - The National Environmental Policy Act formed the nation's basic charter for environmental protection. It directed federal agencies to carry out their functions in a way that avoids or minimizes environmental degradation and required them to conduct planning with studies of potential environmental impact for all development projects. In addition, the planning process would be open for public input. The new environmental legislation significantly increased the complexity of the Service's resource management in the parks.

General Authorities Act, 1970 - The General Authorities Act of August 18, 1970, redefined the National Park System to include all areas managed "for park, monument, historic, parkway, recreational, or other purposes" by the National Park Service. This marked a change from earlier legislation in which Congress legally defined the National Park System to exclude most areas in the recreational category. The legislation declared the various types of parks to be part of a single system.

Endangered Species Act of 1973 - The Endangered Species Act required federal agencies to ensure that their activities (authorized, funded, or executed) do not jeopardize the existence of any endangered or threatened species of plant or animal (including fish) or result in the destruction or deterioration of critical habitat of such species. It also provided for studies to determine endangered or threatened species and stipulates that it is unlawful for a person to possess, export, or import such species. This and other environmental legislation of the 1960s and 1970s served to bolster the role of science in park management.

Redwood National Park Expansion Act, as amended, 1978 - In the 1970s Congress grappled with the problem of the encroachment upon parks by adjacent activities. The coastal Redwoods in Redwood National Park were being threatened by logging activities outside the park boundaries. In 1978, Congress expanded the park boundaries to encompass the remaining watershed and protect the endemic ecosystem. The legislation was in effect a declaration encouraging the protection of national parks from external threats.

National Parks and Recreation Act, 1978 - The Act authorized the additional of 15 units to the National Park System, to include the Santa Monica Mountains National Recreation Area.

Archaeological Resources Protection Act, 1979 - The legislation corrected more than seven decades of inadequate protection for archaeological sites and objects. It superceded Antiquities Act as the prime legislative protection for federal archeological resources by defining them more completely and establishing appropriate penalty provisions for their destruction or theft.

Alaska National Interest Lands Conservation Act, 1980 - The Alaska National Interest Lands Conservation Act added more than 47 million acres to the National Park System. Two years earlier, President Jimmy Carter had proclaimed national monuments totaling roughly 45 million acres in Alaska, greatly expanding the National Park Service's land management responsibilities. The 1980 legislation sanctioned President Carter's action and converted most of the national monuments in Alaska into national parks and preserves. This legislation more than doubled the size of the national park system and dramatically increased the total designated wilderness acreage.

Native American Graves Protection and Repatriation Act, 1990 - Earlier legislation had expressly forbidden the excavation of Indian graves and removal of human and ceremonial remains. This act went further, directing museums to return Indian remains to the direct or at least cultural descendants for reburial. Compliance created some difficulties for museums including those in the National Park Service.

The Vail Agenda, 1992 - In 1992 hundreds of experts from within and outside the National Park Service participated in a conference in to commemorate the Service's seventy-fifth anniversary. The addressed the current status of national park management and made recommendations for the future. Their report, known as the Vail Agenda, addressed the status and needs of the National Parks in the 21st Century. The document reiterated the concerns expressed in the State of the Park Report (1980) and the General Accounting Office Report (1987). Among the recommendations was an urgent call for park management grounded in scientific research.

National Park Omnibus Management Act of 1998 - The broad Omnibus Act provided for improved management and increased accountability for certain National Park Service programs. It directed reform of the process by which areas are considered for addition to the National Park System. Specifically, the legislation provided that no study of the potential of an area for inclusion in the National Park System be made without the specific authorization of Congress. The Omnibus Act also instituted the first legislative reforms of the Service's concessions management practices in a generation. The Service responded with new regulations and guidelines for concessions contracts, commercial use authorization, and the use of franchise fees. It allowed the Service to retain concessions franchise fees in the parks in which they were collected.

Revisiting Leopold Report, August 2012 --- Climate change, biodiversity, and the current state and understanding of ecosystem management all were unknown to A. Starker Leopold 50 years ago when he oversaw a report that became the National Park Service's guide to managing wildlife in the parks. That so-called Leopold Report, though valuable for its time, is now drastically obsolete, so much so that the National Park Service needs to, in essence, reinvent how it approaches scientific study, and management of natural resources, within its nearly 400 parks. That was the message delivered to Park Service Director Jonathan Jarvis on the eve of his agency's 96th birthday.