National Park Service ranger Tad Shay describes the events of the 1944 explosion in front of pilings from the old piers, still visible at the Port Chicago Naval Magazine National Memorial in Concord, Calif. on Saturday, Feb. 7, 2015. The memorial is at th

National Park Service ranger Tad Shay describes the events of the 1944 explosion in front of pilings from the old piers, still visible at the Port Chicago Naval Magazine National Memorial in Concord, Calif. on Saturday, Feb. 7, 2015. The memorial is at the location on Suisun Bay where 320 men were killed after two massive explosions occurred while ships were being loaded with munitions during World War II. Reservations are required two weeks in advance to visit the site, which is operated by the National Park Service. (Photo By Paul Chinn/The San Francisco Chronicle via Getty Images)