Question: What is the population of the area where Slipknot was formed?

full_context: Document 1: Great Big Mouth Records: Great Big Mouth Records is a record label based in Des Moines, Iowa, which was founded by Slipknot and Stone Sour frontman Corey Taylor and Denny Harvey. The label was conceived to help bring attention to Midwestern bands, Taylor explains; "basically we're just trying to unify the scene and really bring more attention to the Midwest than there is right now.".
Document 2: Saylorville, Iowa: Saylorville is a census-designated place (CDP) in Polk County, Iowa, United States. The population was 3,301 at the 2010 census. It is part of the Des Moines–West Des Moines Metropolitan Statistical Area. The Saydel Community School District is located in this area. The unincorporated community of Marquisville is in this area.
Document 3: Squint Entertainment: Squint Entertainment was a record label owned by Word Entertainment, started in 1997 and run by musician and songwriter Steve Taylor. Squint pushed Sixpence None the Richer to mainstream success with their single "Kiss Me". (The band had been in the CCM genre for several years before that). Other successful bands, such as Chevelle, emerged from Squint's brief creative life.
Document 4: Kirtland Records: In 2003, John Kirtland co-founded Kirtland Records with his wife, The Polyphonic Spree choir member Jenny Kirtland. Kirtland Records leveraged the Bush back catalog rights to secure a national distribution deal with RED Distribution, which remains the label's distributor. Kirtland Records went on to become the record label for a number of Texas-based indie bands, including the Burden Brothers, The Polyphonic Spree, Toadies, The Vanished, and Sarah Jaffe.
Document 5: Des Moines, Iowa: Age spread: 24.8% under the age of 18, 10.6% from 18 to 24, 31.8% from 25 to 44, 20.4% from 45 to 64, and 12.4% who were 65 years of age or older. The median age was 34 years. For every 100 females, there were 93.8 males. For every 100 females age 18 and over, there were 90.5 males.
Document 6: Cedar Rapids, Iowa: As of the 2010 United States Census, the city population was 126,326. The estimated population of the three - county Metropolitan Statistical Area, which includes the nearby cities of Marion and Hiawatha, was 255,452 in 2008. Cedar Rapids is an economic hub of the state, located in the core of the Interstate 380.
Document 7: Mike Varney: Mike Varney is an American musician, record producer, music publisher and impresario. He is the founder of the Shrapnel Label Group, which includes Shrapnel Records, Tone Center Records and Blues Bureau International. He also has a 50% stake in Magna Carta Records, a New York-based label. Amazon.com currently lists over 790 albums as being released by record labels founded or owned by Mike Varney. He is often credited with being the individual most responsible for popularizing the mid-1980s shred guitar boom, and has continuously specialized in producing highly acclaimed musicians within the genres of instrumental rock, hard rock, jazz, jazz fusion, blues, blues-rock, progressive metal and speed metal.
Document 8: Kanye West: West founded the record label and production company GOOD Music in 2004, in conjunction with Sony BMG, shortly after releasing his debut album, The College Dropout. John Legend, Common, and West were the label's inaugural artists. The label houses artists including West, Big Sean, Pusha T, Teyana Taylor, Yasiin Bey / Mos Def, D'banj and John Legend, and producers including Hudson Mohawke, Q-Tip, Travis Scott, No I.D., Jeff Bhasker, and S1. GOOD Music has released ten albums certified gold or higher by the Recording Industry Association of America (RIAA). In November 2015, West appointed Pusha T the new president of GOOD Music.
Document 9: Curb Appeal Records: Curb Appeal Records was an American record label founded in Kansas City, Missouri by The Get Up Kids guitarist and Blackpool Lights frontman Jim Suptic.
Document 10: Johnston, Iowa: Johnston is a city in Polk County, Iowa, United States. The population was 17,278 in the 2010 census, an increase of almost 100% from the 8,649 population in the 2000 census. It is part of the Des Moines–West Des Moines Metropolitan Statistical Area.
Document 11: Royal Empire Records: Originating in Washington State during 2001 as REK Squad Entertainment, Royal Empire Records founder Edward Galloway and co-founder Mario Lyons set out on a mission to transcend to the top of the music industry. Although the path was long and the participants in that quest have changed frequently, Edward Galloway's mission has not. In 2003, Edward Galloway & Mario Lyons' vision of a successful record label came to life as Royal Empire Records.
Document 12: To My Surprise: To My Surprise was an American experimental rock band formed in 2002 in Des Moines, Iowa. They are referred to as a side project of Shawn Crahan, a member/founder of heavy metal band Slipknot. In 2003 they released their debut album "To My Surprise", however after losing frontman Brandon Darner in 2004 they parted ways with their record label. 2005 saw four new members join the band to begin work on a second album and in 2006 they began performing shows in the US. However, shortly after To My Surprise canceled several upcoming appearances and disbanded without releasing a second album.
Document 13: Middletown, Iowa: Middletown is a city in Des Moines County, Iowa, United States. The population was 318 at the 2010 census. It is part of the Burlington, IA–IL Micropolitan Statistical Area.
Document 14: Des Moines metropolitan area: The Des Moines metropolitan area, officially known as the Des Moines -- West Des Moines, IA Metropolitan Statistical Area (MSA), consists of five counties in central Iowa, United States: Polk, Dallas, Warren, Madison, and Guthrie. The 2010 census population of these counties was 569,633, and the 2017 estimated population was 645,911.
Document 15: Des Moines, Iowa: On September 22, 1851, Des Moines was incorporated as a city; the charter was approved by voters on October 18. In 1857, the name ``Fort Des Moines ''was shortened to`` Des Moines'', and it was designated as the second state capital, previously at Iowa City. Growth was slow during the Civil War period, but the city exploded in size and importance after a railroad link was completed in 1866.
ground_truth: 645,911
sub_queries: Slipknot >> location of formation Answer: Des Moines
what is the population of the Des Moines area Answer: 645,911