On April 4, 1841, William Henry Harrison became the first US president to die in office.
Harrison's death shocked the nation. He had been inaugurated just 30 days earlier, making him to this day the shortest-serving president in US history.
Harrison is commonly believed to have died of pneumonia caught while giving his famously long Inaugural Address — although that theory is disputed by some modern historians.
It took several days for the news of Harrison's death to spread across the country, as evidenced by newspaper archives available on the Library of Congress' website.
The unprecedented death of a sitting president caused a brief crisis, as the Constitution did not specify how much power the vice president should get in such a situation. Some believed Tyler should serve merely as "acting President," although Tyler quickly established his right to fully succeed Harrison, setting future precedent that eventually inspired the 25th Amendment.
That didn't stop critics from giving Tyler the unfortunate nickname "His Accidency."