Growing up, George E. Raley Jr. heard stories that the military had conducted some sort of testing during World War II on the quiet Southern Maryland peninsula known as Newtowne Neck.

As an adult, he would learn that his father had assisted in experiments performed by the Johns Hopkins University Applied Physics Laboratory to develop a weapon credited with helping the Allies win the war in Europe.

So he was not particularly surprised this month when the sands of the peninsula where he once camped, swam and picked blackberries shifted to reveal a small but substantial stockpile of World War II-era munitions.

"Not surprised," Raley said. "But very interested."

Authorities, alerted by a local woman who came across a 57 mm ammunition round while strolling on the beach on New Year's Day, have found 27 pieces of suspected military ordnance along the shoreline of what is now Newtowne Neck State Park.

Military bomb experts have detonated the vintage munitions, and the Army Corps of Engineers is combing land records and military archives to determine how they got here. Meanwhile, the Maryland Park Service has closed Newtowne Neck until further notice.

"From the information we have so far, we do not expect this to be a permanent situation, but we don't know the duration of the closure," Lt. Col. Christopher Bushman, the deputy superintendent of state parks, said Friday. "Public safety is the priority."

The live rounds that are believed to have lain buried here for close to 70 years were only the latest unexploded military ordnance to turn up around the Chesapeake Bay in recent years. From Aberdeen Proving Ground to the Hampton Roads area of Virginia, the region has seen decades of munitions testing.

Pooles Island, a rocky outcropping east of Baltimore that was used from World War I to the 1960s for target practice, has been declared off-limits to the public because of the danger of unexploded ordnance, as has most of the Plum Tree Island National Wildlife Refuge in Virginia.

The surge from Tropical Storm Isabel in 2003 carried bombs and shells ashore. Nautical charts of the bay warn sailors of live depth charges and other munitions still in the water.

Live munitions still are found most commonly in "grandpa's attic," according to Deputy State Fire Marshal Bruce Bouch. But ordnance encountered in or around the water, he said, poses a special risk.

"We have to take it seriously," Bouch said. "They have been underwater, they've been infiltrated with salt water, they're highly unstable. The potential is there for great harm or death."

Bouch said the woman who found the shell on the beach at Newtowne Neck on New Year's Day went home and described it to her husband. They then called 911.

The peninsula, site of the second European settlement in Maryland after St. Mary's City, protrudes into the Potomac River near the Chesapeake Bay. The land was maintained by the Society of Jesus from the 1660s until 1967.

For much of that time, the Jesuits leased it for farming. But during World War II, it was used by the Applied Physics Laboratory in Silver Spring to develop and test the proximity fuse, a top-secret effort that historians have compared to the atomic bomb-building Manhattan Project.

The fuse, intended initially to help the Allies defend against German rockets, caused an artillery shell to detonate as it approached a target. That meant it was no longer necessary to score a direct hit to stop an incoming rocket; close was good enough.

The innovation helped neutralize German V-1 attacks on England and Japanese kamikaze attacks in the Pacific. Eventually used in land warfare, the fuse was credited by Gen. George S. Patton with winning the Battle of the Bulge.

"The VT or radio proximity fuse as finally produced in this country during the war was the greatest invention in artillery since the explosive shell," journalist Lee McCardell wrote in the Sun Magazine in November 1945. "As a secret weapon, it ran second in importance to the atomic bomb only."

When Raley was playing soldiers with friends in the 1950s, his father told him about the proximity fuse. Raley himself had seen the observation towers at Newtowne Neck.

But it wasn't until after his father's death in 2004 that Raley learned that he had been involved in the testing — the family found a 1943 letter from his supervisor at the Applied Physics Laboratory praising his work. George E. Raley Sr. is listed among the project's participants in "The Deadly Fuze: Secret Weapon of World War II," a 1980 book by Hopkins physicist Ralph Belknap Baldwin.