April 17-25 is National Park Week, with free entrance to 392 sites administered by the National Park Service. But, if you do your research, you can find free national parks year-round: 246 park properties—including national monuments, historic sites, and battlefields—never charge admission.
Waived fees next week may not have much financial impact at, say, Pinnacles National Monument in California, where vehicle admission is $5, but they could well make a difference in a family’s ability to see Grand Canyon National Park, where the normal rate is $25 per vehicle.
Of the 58 sites with national park designation (not monuments, historical sites, and other properties in the national parks system), four, including Gates of the Arctic, lie in remote, roadless Alaska. Gates, which is always free, saw just 11,397 registered visitors in 2008, making it the fifth least-visited national park that year.
Mel White is the author of National Geographic's Complete National Parks of the United States, released in February 2010.