She checked in to the hospital 23 weeks into her pregnancy and gave birth seven weeks later.
A spokeswoman at the Bellflower medical centre described the deliveries, which took place in the space of five minutes, as "truly amazing".
The medical team had scheduled a Caesarean section for seven babies, but doctors were surprised when an eighth came out.
"Lo and behold, after we got to Baby G, which is what we expected, we were surprised by Baby H," said Dr Karen Maples.
Three of the babies needed help breathing, but all were otherwise doing well, a doctor said.
The babies will be in incubators for at least six weeks and the mother is planning to breast feed them all, the hospital officials said.
"She is a very strong woman, so she probably will be able to handle all eight babies," said Dr Mandhir Gupta.
He added that the mother was "doing very, very well" and was "really excited that she got all of these babies, and that they're doing good so far".
The team did not give any more details about the mother's identity or say whether she had used fertility drugs.