Question: What county contains Clayton in the US state having Knoxville Raceway?

full_context: Document 1: Everly, Iowa: Everly is a city in Clay County, Iowa, United States. The population was 603 in the 2010 census, a decline from 647 in the 2000 census. The Ocheyedan River flows to the south and west of the city.
Document 2: Clayton Township, Adams County, Illinois: Clayton Township is one of twenty-two townships in Adams County, Illinois, United States. As of the 2010 census, its population was 1,027 and it contained 465 housing units.
Document 3: Beaver Dam Raceway: Beaver Dam Raceway is a one-third mile banked clay oval track located in Beaver Dam, Wisconsin, U.S.A.. The track holds weekly races over the Northern American summer months. It hosts an annual World of Outlaws sprint car races. The 2013 U.S. Dirt Legends Nationals event was held at the track.
Document 4: Clayton, Iowa: Clayton is a city in Clayton County, Iowa, United States. The population was 43 at the 2010 census, down from 55 at the 2000 census. Clayton is located directly on the Mississippi River and is only accessible by a very steep road. Many people have summer homes in Clayton due to its proximity to the Mississippi River.
Document 5: Clayton Township, Perry County, Ohio: Clayton Township is one of the fourteen townships of Perry County, Ohio, United States. The 2000 census found 1,432 people in the township.
Document 6: Clay City Township, Clay County, Illinois: Clay City Township is one of twelve townships in Clay County, Illinois, USA. As of the 2010 census, its population was 1,287 and it contained 649 housing units.
Document 7: Summit Township, Clay County, Iowa: Summit Township is a township in Clay County, Iowa, USA. As of the 2000 census, its population was 452. Spencer Municipal Airport is located in the township.
Document 8: Potomac Speedway: Potomac Speedway is a 3/8 mile clay oval raceway located in Budds Creek, Maryland, near Charlotte Hall. The raceway was first raced on in 1973. Races are typically held on Friday or Saturday nights. Regular events include Super Late Models, Limited Late Models, Street Stocks, and Hobby Stocks and 4 cylinders. The speedway also holds events for Modifieds, Crate Late Models, Strictly Stocks and Hornets. Potomac Speedway has a seating capacity of about 4,000 in the main grandstands and can hold an additional 1,000 in the pit area.
Document 9: Dow City, Iowa: Dow City is a city in Crawford County, Iowa, United States, along the Boyer River. The population was 510 at the 2010 census.
Document 10: Tucson, Arizona: Tracks include Tucson Raceway Park and Rillito Downs. Tucson Raceway Park hosts NASCAR-sanctioned auto racing events and is one of only two asphalt short tracks in Arizona. Rillito Downs is an in-town destination on weekends in January and February each year. This historic track held the first organized quarter horse races in the world, and they are still racing there. The racetrack is threatened by development. The Moltacqua racetrack, was another historic horse racetrack located on what is now Sabino Canyon Road and Vactor Ranch Trail, but it no longer exists.
Document 11: Knoxville Raceway: Knoxville Raceway is a semi-banked 1/2 mile dirt oval raceway (zook clay) located at the Marion County Fairgrounds in Knoxville, Iowa, United States. Races at the "Sprint Car Capital of the World" are held on Saturday nights from April through September each year. Some special events may start as early as Wednesday and build up to Saturday. Regular events include 305 cubic inch, 360 cubic inch and 410 cubic inch sprint car racing. Each August, the Raceway holds the paramount sprint car event in the United States, the Knoxville Nationals. The track is governed by the 24-member fair board elected by Marion County residents.
Document 12: Bristol Motor Speedway: Bristol Motor Speedway, formerly known as Bristol International Raceway and Bristol Raceway, is a NASCAR short track venue located in Bristol, Tennessee. Constructed in 1960, it held its first NASCAR race on July 30, 1961. Despite its short length, Bristol is among the most popular tracks on the NASCAR schedule because of its distinct features, which include extraordinarily steep banking, an all concrete surface, two pit roads, and stadium - like seating. It has also been named one of the loudest NASCAR tracks.
Document 13: Exhibition game: Various auto racing organizations hold exhibition events; these events usually award no championship points to participants, but they do offer prize money to participants. The NASCAR Sprint Cup Series holds two exhibition events annually - the Sprint Unlimited, held at Daytona International Speedway at the start of the season, and the NASCAR Sprint All-Star Race, held at Charlotte Motor Speedway midway through the season. Both events carry a hefty purse of over USD $1,000,000. NASCAR has also held exhibition races at Suzuka Circuit and Twin Ring Motegi in Japan and Calder Park Thunderdome in Australia.
Document 14: Clayton, Missouri: Clayton is a city in and the county seat of St. Louis County, Missouri, United States, and borders the city of St. Louis. The population was 15,939 at the 2010 census. The city was organized in 1877 and is named after Ralph Clayton, who donated the land for the courthouse. The city is known for its multiple skyscrapers in its business district.
Document 15: Cornwall Motor Speedway: The Cornwall Motor Speedway is a 1/4 mile dirt track near the community of Cornwall, Ontario, Canada. It is located northwest of the city on Cornwall Centre Road. The track opened in 1970 and runs weekly racing on Sunday evenings.
ground_truth: Clayton County
sub_queries: In which state is Knoxville Raceway located? Answer: Iowa
Clayton, Iowa >> located in the administrative territorial entity Answer: Clayton County