The incident happened Friday near Balsam Road just north of Lone Eagle Street.
Dejuan Rene Smith was pushing her 14-month-old daughter in a stroller when a Ford pickup truck hit her from behind, officials said.
Smith died at the scene. Her daughter suffered minor injuries after being thrown from the stroller.
Smith's family is asking for the suspect to come forward.
"Please turn yourself in. I mean, you left my niece without a mom," said Sandy Underwood, the victim's sister. "This is devastating to all of us."
Investigators said the truck will likely have right front-end damage, and it's missing the mirror on the passenger side.
Anyone with information was asked to call the San Bernardino County Sheriff's Department at (760) 241-2911.