President Barack Obama has signed into law a bill that will allow Petersburg National Battlefield to expand and become the nation's largest protected battlefield. The park commemorates climactic sites in the Civil War's longest battlefield conflict, spanning some ten months between 1864 and 1865. Legislation signed days ago by President Obama authorizes the addition of more than 7,000 acres to the existing 2,700 acres of rolling hills, earthworks and siege lines already under protection at Petersburg.