Ms Baines was believed to have been the oldest African-American voter
The oldest person in the world has died in Los Angeles at the age of 115 of suspected heart failure.
Gertrude Baines, born 6 April 1894, had held the title since January, when a Portuguese woman, Maria de Jesus, died, also at the age of 115.
Ms Baines's doctor said she had attributed her long life to a healthy lifestyle and her religious beliefs.
The title of world's oldest person now passes to a 114-year-old Japanese woman, Kama Chinen.
Officials at the Western Convalescent Hospital, where Ms Baines had lived for several years, said she had died at 0725 local time (1425GMT).
"She told me that she owes her longevity to the Lord, that she never did drink, she never did smoke and she never did fool around," the AFP news agency quoted Dr Charles Witt as saying.
He said two days before her death she had been "in excellent shape".
"She was mentally alert. She smiled frequently," he said.
Ms Baines, whose father was once a slave, was believed to be the oldest ever African-American voter when she cast her ballot for US President Barack Obama in November 2008.
She said she was voting for him "because he's for the coloured people".
She celebrated her 115th birthday in April and received a letter of congratulations from Mr Obama.
Gertrude Baines at her 115th birthday party
Gertrude Baines, the world's oldest person, died aged 115 in Los Angeles, California on Friday.  The suspected cause of death is heart failure.

"She passed away this morning at 07.25 14.25 UTC," said administrator Emma Camanag of the Western 
Convalescent Hospital.

Baines, who was born on April 6, 1894, became the world's oldest person in January this year, after 
Maria de Jesus, a Portuguese woman, died aged 115.

Charles Witt, Baines' doctor, said, "she told me that she owes her longevity to the Lord, that she never did drink, she never did smoke and she never did fool around," according to the Agence France-
Presse news agency.

"She was mentally alert. She smiled frequently," he said.

The oldest person in the world is now Kama Chinen, a woman from Japan.