A simple stone marker on a Southern California golf course marks the spot where a Japanese submarine tried to take out an oil field at the beginning of World War II. It didn’t succeed, but the attack tragically hastened the government’s plan to round up more than 100,000 Japanese-Americans and place them in internment camps.

It was a little after 7 p.m. on February 23, 1942, in the small town of Goleta, about 10 miles up the coast from Santa Barbara. Ten-year-old J.J. Hollister and his family had just settled in to listen to President Roosevelt on the radio, when the boy thought he heard thunder. There was a thump, and J.J. and his family ran outside to find bright flashes lighting up the Ellwood Oil Field, just off shore.

A Japanese submarine was shelling Goleta, in the hope of destroying the oil installations. Unlike other oil fields on the California coast, Ellwood had no military protection, making it an easy target. In all, a dozen or two shells landed on Goleta, but little physical damage was done. Instead, the toll of the attack fell on the national psyche, with headlines crying “Submarine Shells Southland Oilfield,” and “First Attack of War on Continental U.S.”

The panic created by the attack at Ellwood sparked what became known as the “Battle of Los Angeles,” when the following night saw a barrage of defensive anti-aircraft fire by the U.S. military, an overreaction to the spotting of an innocent weather balloon.

Today two markers along the Santa Barbara Channel commemorate this rare attack on the continental United States: a stone in the middle of the Sandpiper Golf Course, and a small wooden sign a quarter mile away at Haskell’s Beach.