GETTYSBURG, Pa. -- Thousands of people have gathered at Gettysburg National Military Park for a service commemorating the 150th anniversary of the fierce battle that proved to be the turning point of the American Civil War.

National Park Service director Jonathan Jarvis told attendees Sunday night the weeklong events are intended to honor the dead, and recognize the courage and heroism of the soldiers who fought at Gettysburg from July 1-3, 1863.

He says visitors have also gathered to reaffirm the principles that demanded the terrible sacrifices Union and Confederate soldiers made 150 years ago.

Historian and author Doris Kearns Goodwin delivered the keynote address. Her best-selling novel "Team of Rivals" in part inspired last year's Oscar-winning film "Lincoln."

The ceremony was scheduled to conclude with a procession to Soldiers National Cemetery.

GENARO C. ARMAS, Associated Press