On October 3, 1849, Edgar Allan Poe was found on the streets of Baltimore in disarray.

“He’s muttering a variety of things that are indecipherable. Nobody really knows who he is, and he’s not wearing his own clothes,” says David C. Ward, a historian at the National Portrait Gallery. “It seems pretty clear that he was suffering from some sort of alcohol or drug overdose.”

By age 40, Poe had written reams of poetry, attempted to start his own literary journal and become one of the first Americans to support oneself strictly as a writer. But eventually, his mental illnesses and alcohol abuse caught up with him. “He’s wandering around and they put him in the charity hospital, and he suffers four days of what must have been fairly awful trouble,” Ward says. On this day in 1849, America lost one of its most innovative and unusual literary figures to a death as mysterious as his life and works.

He was born to David and Elizabeth Poe, both Boston actors, in 1809, but his father abandoned the family when Edgar was just a year old, and his mother died soon thereafter of tuberculosis. He was taken into the home of the Allans, a wealthy Virginia family, but things continued going downhill for little Edgar from there. “He had a very tempestuous relationship with his surrogate father,” says Ward. After spending an uneasy childhood in both Virginia and Britain, Poe left home to attend the University of Virginia, where he only lasted a year.

“He ran up large gambling debts, and Mr. Allan refused to pay them, so Poe drops out,” says Ward. “Ultimately, Allan rejects Poe, so there’s this element of double rejection in his life.”

After a stint as a cadet at West Point, Poe decided to devote his life to becoming a writer. “He is the first American who tried to make a living just simply by writing,” says Ward. “At the time, the other writers were usually ministers, or professors.” Over the next two decades, he obsessively crafted dark, mysterious poetry, then turned to short stories in a similar vein.

Deeply critical of contemporary literature, he held posts at various literary journals and discussed plans to start his own. Transcendentalism was one of the most prominent literary and philosophical concepts of the day, and held that individual spirituality and a connection to nature could provide meaning and insight to anyone. “He hated transcendentalism—he thought that it was just moonshine and propaganda,” Ward says. “He hated Longfellow, the preeminent poet of the day, who he saw as a fraud.”

During this time, he secretly married his first cousin, Virginia Clem. “He marries his 13-year-old cousin, which is, to be blunt, a little bit creepy,” says Ward. Soon, she too would suffer from tuberculosis, leading many to speculate that the presence of even more misery in his life further contributed to the nightmarish focus of his work.

Poe’s fixation with the macabre and gruesome cut completely against the grain of 19th-century American literature. His stories typically featured death, corpses and mourning. “Poe is totally against everything that America seemed to stand for. He’s dark, inward-turning and cerebral. Death-obsessed instead of life-obsessed,” Ward notes. “If Whitman is the poet of the open road, Poe is the poet of the closed room, of the grave.”

Poe became a household name with the publication of the poem “The Raven” in 1845, but his lasting influence is evident in a number of genres. “In 1841, be basically invents the detective story, with The Murders in the Rue Morgue,’ Ward says. “His detective, Dupin, is the forerunner of Sherlock Holmes: he’s a cerebral, brainiac detective who solves problems by his brain powers.” Other stories influenced Jules Verne, leading to the emergence of the genre of science fiction.

The 1847 death of Virginia, coupled with Poe’s increasingly heavy drinking, pushed him ever further into despair. But even in his final moments, he handed over a mystery, one that his fans have puzzled over for more than a century.

“The kicker to all this is that Poe supposedly left a large trunk of his archives, and that has disappeared,” Ward says. “Poe, the inventor of the mystery story, leaves this trunk behind that we would think might provide a clue to his life, but disappears. It’s this final tantalizing mystery.”