Random Riddle: Death Cured?

My great-grandmother was exceptional from first to last. She was the first baby born in the state in 1851. She was almost the first centenarian in the family, but she died in 1950, one day before her 100th birthday.

The cause of her death was not unusual; thousands of people died of the same cause that year and also in previous years. Her death was exceptional because she was the last person ever to die from that cause in the United States.

What was the cause of death?
 

Random Riddle: Death Cured?