Lower Hudson River Valley"There are many areas in the country that deserve national park status," Kristen Brengel, legislative director of the National Parks Conservation Association, said on the eve of National Park Week, when all U.S. National Parks will waive admission fees. "Secretary [Ken] Salazar of the Interior Department, in particular, is a huge parks advocate."Salazar designated a new national recreation trail in New York State's Hudson River Valley in September. But in March 2010 the U.S. House of Representatives passed a bill asking the National Park Service to consider adding an entire 182-mile (293-kilometer) southern stretch of the scenic valley to the national park system.Parks and historic sites—including Vanderbilt and Rockefeller mansions and Storm King State Park—already dot the area, so any national park designation would have to be a hybrid of jurisdictions. One model might be Mississippi National River and Recreation Area, which encompasses 72 miles (116 kilometers) of the Mississippi around Minneapolis and St. Paul and combines the efforts of federal, state, county, and municipal agencies.(Also see "Pictures: Hidden U.S. Park Gems—Free Next Week and Year-Round.")

—Mel WhiteMel White is the author of National Geographic's Complete National Parks of the United States, released in February 2010.

Photograph by Melissa Farlow, National Geographic