Cortner was active on the midget car racing circuit, with a career spanning ten years. He was the outdoor champion of the Bay Cities Racing Association in 1957, and was inducted into the association's hall of fame in 2007.
On Monday, May 18, Cortner passed the rookie test for the Indianapolis 500, allowing him to attempt to qualify a car for the race, which was to be held May 30. On Tuesday when Cortner took to the track, Johnny Parsons, who observed the accident, reported that the wind was blowing harder than he had ever seen it blow at the track. Parsons stated that the car was caught in a cross wind, and first came into the infield before shooting back across the track head-first into the outer wall. Cortner's face hit the steering wheel and it appeared he began bleeding internally. He was pronounced dead that evening, the cause being listed as "massive head injuries". A number of other drivers were waiting to donate blood to Cortner when the announcement came that he had died. It was the second death at the speedway that year, as Jerry Unser had died in an accident May 2, and the fiftieth death overall in the history of the speedway, occurring in its fiftieth year of operation.
Cortner was married with no children. He is buried at the Hillside Memorial Park cemetery in his home town of Redlands, California.
- Bay Cities Racing Association champions by year
- Bay Cities Racing Association Hall of Fame inductees by year
- Bob Cortner dies after Auto Wreck Associated Press as reported in The News and Courier of Charleston, South Carolina, May 20, 1959
- Second 500 Death Baffles Officials United Press International as reported in the Pittsburgh Press, May 20th, 1959
- Bob Cortner Dies of Head Injuries Suffered in Indianapolis Practice Run by Dale Burgess, Associated Press, as reported in the Youngstown Vindicator, May 20th, 1959
- Robert Charles Cortner at Find A Grave