The official word, from Rivers' friends and employers at E!:

Joan Rivers has passed away at 81 years old. Her daughter, Melissa Rivers, released the following statement: "It is with great sadness that I announce the death of my mother. She passed peacefully at 1:17pm surrounded by family and close friends. My son and I would like to thank the doctors, nurses, and staff of Mount Sinai Hospital for the amazing care they provided for my mother."

RIP Joan Rivers, who is and will remain an entertainment legend. She was also a study in contradictions. As a female stand-up in the 1960s, she blazed a trail that inspired and enabled such contemporary comic miracle workers as Amy Schumer and Sarah Silverman, then, as a New York Times-bestselling author, she turned slut-shaming into a popular art form. She was emotionally open enough to respond to the suicide of her husband by making a TV movie about it starring herself and her daughter as themselves, and emotionally coarse enough to devote the later part of her career to making shitty comments and "jokes" that painted her as the entertainment-television equivalent of Rush Limbaugh.

But as the 2010 documentary Joan Rivers: Piece of Work made clear, she was, more than anything, an inexhaustible comedy professional. As I wrote in my unfortunately titled review of the film:

Incorporating archival footage into the yearlong video diary, the filmmakers do right by Rivers's formidable comic legacy as a fearless, incomparably ambitious woman thrusting herself into the overwhelmingly male world of standup. (Her career-altering relationship with Johnny Carson, who made her a star before shunning her as a competitor, is tracked in all its mindfucky glory.) But the film, like Rivers's life, is all about forward motion—the next gig, the next laugh, the next humiliation en route to a paycheck. (See her Comedy Central roast, here presented as a lucrative, fully legal torture session.) What sticks with you is the depth of Rivers's creative compulsion: So great is her need to perform, that she'll get her fix wherever she can, from run-down New York nightclubs to The Celebrity Apprentice. It's an amazing, exhausting thing to behold.

Happy trails, Joan Rivers. In remembrance, here's one of her many remarkable appearances on Johnny Carson's Tonight Show: