The 1975 Delaware 500 was held at Dover International Speedway on September 14, 1975, before a crowd of 21,000. A field of 37 cars took the green flag, with Dave Marcis winning the pole position at 133.953 mph. The race was slowed by five caution flags for 41 laps.
Richard Petty appeared headed for a dominant victory, almost two full laps ahead when a broken tie rod on lap 348 forced him to make lengthy repairs and dropped him six laps behind the leaders. With Petty sidelined, Cale Yarborough appeared headed for victory with a four-lap lead until he lost two cylinders that left the race to be decided by Dick Brooks and Benny Parsons. Petty had recovered five of his lost laps but still remained one lap down late in the race.
The turning point came when Buddy Arrington stopped his car on the racing surface, bringing out a controversial caution flag. The caution allowed Petty to regain the final lap and return to the lead lap. Once back in contention, Petty charged through the field and reclaimed the lead with eight laps remaining. He took the checkered flag by 1.3 seconds over Dick Brooks, with Benny Parsons finishing third. Cale Yarborough was fourth despite engine problems late in the event, and Bruce Hill completed the top five.
