The morning after two million pounds of munitions exploded in New York Harbor on July 30, 1916, killing five people, jostling the Brooklyn Bridge, shattering plate-glass windows six miles away and shaking building foundations in five states, law enforcement officials all but ruled out a terrorist attack by Germans. Decades later, dogged investigations proved them wrong.

No individuals were ever convicted in the attack that summer Sunday as World War I raged in Europe, but in 1939, an international claims commission reversed itself and declared the German government legally accountable for the damage. And, finally, four decades after that, the post-World War II government in Bonn paid the last installment of a $50 million award for reparations.

The explosion on Black Tom Island, a 25-acre promontory jutting from Jersey City that was built from New Yorkers’ garbage, registered an estimated 5.5 on the Richter scale — 30 times more powerful than the collapse of the World Trade Center 85 years later. It was considered the most destructive terrorist attack in America until Sept. 11, 2001.

The blast occurred the day before Charles Evans Hughes, a former governor of New York, was to formally accept the Republican presidential nomination in a speech at Carnegie Hall and confront Woodrow Wilson, whose re-election campaign slogan, “He kept us out of war,” would be abrogated the following April when Congress declared war on the German Empire.