Legislation introduced to the U.S. Senate aims to add 7,200 acres to Petersburg National Battlefield, a bid that, if approved, would make Petersburg the largest military park in the country while protecting a dozen Civil War-era battlefields.

The most popular national parks get visitors galore. Let's have a look at the other end of the attendance spectrum, the end that is anchored by the least-visited parks in the system.

For years visitors to Mesa Verde National Park were largely limited to touring cliff dwellings atop Chapin Mesa. Now, however, four ranger-guided hikes have been added to the possibilities of exploring Mesa Verde.

The caves and visitor center at Timpanogos Cave National Monument in Utah close each winter and usually reopen for the season in early May. If you're planning a visit this year, be aware that schedule will change for 2011 to allow for completion of several projects to improve visitor and employee safety.