The Aspen Dental Eldora Dirt Derby is a 75-mile-long (121 km) annual race in the NASCAR Camping World Truck Series race held at Eldora Speedway in Rossburg, Ohio.
On November 28, 2012, NASCAR announced the addition of a race at Eldora Speedway to the 2013 NASCAR Camping World Truck Series's schedule. The race would be the first on a dirt surface in any of NASCAR's national touring series (Cup, Nationwide, or Truck) since 1970, with the last being at the North Carolina State Fairgrounds in Raleigh, North Carolina.
The inaugural running of the event, which completely sold out in January 2013, was run on July 24, 2013. Austin Dillon won the event after retaining the lead on a green–white–checker finish.
For the 2016 edition, the event was tentative renamed to the #Eldora at Eldora Speedway, following a trademark dispute with Major League Baseball over use of the name "Mudsummer Classic", as the league's All-Star Game is marketed as the "Midsummer Classic". After acquiring sponsorship from Aspen Dental, the event was formally named the Aspen Dental Eldora Dirt Derby.
There are five qualifying races, consisting of ten laps each, that determine the starting grid. However, driver's starting positions in the qualifying races are determined by normal two-lap qualifying sessions. Caution laps in the qualifying races are not scored, and five trucks will transfer from each qualifying race. After the five races, a total of 25 trucks will have qualified for the feature (the main event). Another race, named the 'Last Chance Race', consists of 15 laps, and determines the lineup from position 26 to 29. The final position on the grid is awarded to the most recent Camping World Truck Series champion, unless there is no beneficiary to that position. In that case, the fifth-place finisher in the 'Last Chance Race' is awarded the final starting position. The main event, or feature, is 150 laps long, with three segments of 60, 50, and 40 laps. During each break, drivers are allowed to make pit stops.
In 2014, the format was changed. Instead of lasting eight laps, the heat races will now consist of ten laps, with the top five teams failing to qualify for the Main Feature being awarded owners' points. Additionally, drivers are no longer required to pit.2013 and 2015: This race was extended due to a NASCAR Overtime finish.
The Tuesday Night Tailgate is the supporting event to the Mudsummer Classic featuring pre-race technical inspection for the Truck Series teams. From 2014 to 2015, the event included the Sunoco American Late Model Series. In 2016, the event will feature the Super DIRTcar Series Big Block Modifieds, which will return to Eldora for the first time since 2006.