On a late-winter afternoon in 1844, a giant cannon named "Peacemaker" exploded on the deck of the Navy steam frigate Princeton, killing the secretary of State and the Navy's civilian chief.
The disaster jolted the young republic. But not all of the consequences were tragic.
Aboard the newly launched Princeton were President John Tyler and 400 guests representing the capital's social and political elite. They included Cabinet members, senators, representatives, senior Navy officers, social leaders, foreign envoys, their wives and the nation's most celebrated woman, former first lady Dolley Madison.
Tyler, at 54, was a recent widower, and one of his guests was a much younger woman who had turned his head. She was 24-year-old Julia Gardiner, accompanied by her father, wealthy New Yorker David Gardiner.
She had recently rejected the president's proposal of marriage. He hoped she would reconsider.
The weather on Feb. 28, 1844, was pleasant, "almost a summer sky," someone called it, as the Princeton left its berth at Alexandria, Va., and steamed down the Potomac toward Mount Vernon.
Throughout the morning Navy officers kept their guests entertained by test-firing the new Peacemaker, a 13-ton monster said to be the world's largest naval gun. It fired 225-pound iron cannonballs, which bounded downriver.
In the afternoon, the ship turned back toward the capital. At 3 p.m. it was off Ft. Washington on the Maryland shore when the request came to load and fire the Peacemaker just one more time.
By this time most passengers, including the president and Julia Gardiner, were below deck.
At least one high-ranking passenger walked away moments before the cannon was fired.
"Though I am secretary of War, I am afraid of these big guns," William Wilkins was heard to say.
When Peacemaker was fired, the breech burst. A large fragment of jagged metal hurtled backward into the knot of spectators, killing eight.
The casualty list included Secretary of State Abel P. Upshur, Navy Secretary Thomas W. Gilmer, two other government officials and Julia Gardiner's father.
When the ship reached Alexandria, President Tyler scooped up the distraught Julia Gardiner in his arms and carried her across a gangplank to another vessel.
More than 40 years later, she described the scene to journalist Nelly Bly: "I fainted and did not revive until someone was carrying me off the boat, and I struggled so that I almost knocked us both off the gangplank" into the icy water.
In the aftermath of the Peacemaker explosion, the Navy hastened to improve its system for assuring the quality of its ordnance.
And the May-December romance between the New York heiress and the president of the United States took wing. They became secretly engaged. In June they exchanged vows in a private ceremony in Manhattan.
With her new husband's presidency approaching its end, Julia Gardiner Tyler launched an eight-month whirl as first lady.
"Life at the White House had suddenly never seemed merrier," historian William Seale reports in "The President's House," his history of the nation's presidential families. "The new Mrs. Tyler liked to sing and dance; she liked luncheons, morning cruises on the river and fancy dress balls."
One ball consumed 1,000 candles and 96 bottles of champagne. At another, Mrs. Tyler introduced the polka, "which overnight altered the funerary reputation of the East Room" and quickly became a national rage, Seale writes.
"Now they cannot say I am a president without a party," Tyler quipped.
At Julia Tyler's request, the Marine Band began to play "Hail to the Chief" whenever the president entered the room at a public event, a custom that still endures.
The first lady adopted her husband's crusade to make the Republic of Texas a state. He credited her lobbying campaign with winning majorities in the House and Senate to the cause of Texas statehood.