To do so, she played a cat-and-mouse game for more than three decades with the United States Park Police, which prohibits demonstrators from sleeping on its property or leaving a protest site unattended. When she left to rest, volunteers would relieve her.

That system broke down one day in 2013 when she took a break to grab a bite at a nearby headquarters for peace advocates and her scheduled stand-ins failed to show up. The park police moved in, took down her protest site and got rid of her signs. But after Ms. Norton intervened, Ms. Picciotto was allowed to retrieve her belongings and return to her camp.

In interviews, Ms. Picciotto said she had been orphaned in Spain and raised by a grandmother. After arriving in the United States in 1960, she worked as a receptionist for a Spanish government commercial attaché in New York. She and an Italian immigrant she married (his name could not be learned) lived in the Gravesend section of Brooklyn and adopted an infant daughter, Olga, in Argentina in 1973.

Ms. Picciotto said her husband had committed her to mental institutions to mask his nefarious dealings, which she did not specify, involving the adoption. Eventually, she was released, lost her daughter in a custody dispute and wound up in Washington, where she gravitated to William Thomas, who was conducting his own peace vigil along Pennsylvania Avenue. They were joined in 1984 by Ellen Benjamin, who became Mr. Thomas’s wife. He died in 2009.

Ms. Stribling, who runs the women’s shelter, said Ms. Picciotto had visited the vigil site as recently as last Wednesday. Ms. Picciotto was ailing, she said, but after breaking her arm in a fall, she ignored a doctor’s advice to go to an emergency room.

Ms. Stribling said the medical examiner’s office would probably seek out Ms. Picciotto’s former husband and daughter. She said she expected that Ms. Picciotto’s friends would gather for a memorial service and make sure that she was not buried in a pauper’s grave.

Ms. Picciotto was, by most standards, eccentric, typically clad in a wig, helmet and head scarf as she proselytized for peace, “to stop the world from being destroyed,” while also complaining about unspecified persecution and conspiracies. Was she sane?