national park

Yosemite National Park, in east central California, was established in the 1890s. It now has an area of 300,035 ha/761,170 acres, and the scenery varies from mountains to broad valleys cut by streams and fed by spectacular waterfalls.

Sunrise over the Grand Canyon, Arizona. Reaching depths of over 1.6 km/1 mi, the Grand Canyon National Park is one of the most popular in the US national park system, with many trails for hiking, mule riding, and trips on the river by boat or raft. The varying tones of the different layers of rock change with the light throughout the day.

Land set aside and conserved for public enjoyment. National parks include not only the most scenic places, but also places distinguished for their historic, prehistoric, or scientific interest, or for their superior recreational assets. They range from areas the size of small countries to pockets of just a few acres. The first such designated area in the USA was Yellowstone National Park, established in 1872, although Yosemite National Park, originally a state reserve, predates it.

All elements of the National Park System are under the control of the Department of the Interior. For the most part, they were created from public lands, although since 1925 the government has been empowered to accept donations of land from other sources.

There are more than 300 units in the system. They include:

national monuments, which are generally smaller and display less diversity than national parks, tending to focus on one site, geologic formation, or structure of historic importance; these may be proclaimed by the president, while establishment of a park requires an act of Congress;

national historic sites, national memorials, national military parks, national battlefield parks, and national battlefield sites, which all preserve discrete sites of varied historic importance;

national seashores, national lakeshores, and national rivers, which have been established with the greatest emphasis placed on conservation;

national recreation areas, which are zones near major cities or near certain engineering sites (dams, for example) that have been reserved especially for recreational use in densely populated areas;

national parkways, which are roadways that have been preserved for their scenic value;

national scenic trails, national historic trails, national recreational trails, and other affiliated units are elements of the National Trails System of 1968, which were established to preserve and maintain a wide variety of public footpaths.

In December 1999 a report issued by an environmental group based in Maryland stated that US National Parks are becoming a health risk due to air pollution from nearby coal-burning power plants. On some days throughout 1999, the report claimed, the air quality violated federal standards, posing a risk of respiratory problems such as asthma.

Threatened marine resources at Florida's Dry Tortugas National Park would be protected under a management plan approved in July 2001 by US secretary of the interior Gale Norton. The plan would protect coral reefs, fish habitats, and turtle nesting grounds, with half the park out of bounds to fishers, many of whom had opposed the restrictions. The park is in the Gulf of Mexico about 112 km/70 mi west of Key West, Florida.