Try to name reliable classic lines in the United States, and a couple immediately come to mind: Kentucky Derby winner Unbridled, who has founded a strong branch of the family tree for his grandsire, the prolific Mr. Prospector, and Belmont Stakes winner A.P. Indy, who represents Triple Crown winner Seattle Slew’s branch of the Bold Ruler line. Both are solidly represented in a Kentucky Derby field that is extremely hard to pick apart on pedigree. Messier is by Empire Maker, while both Pioneer of Medina and Tawny Port are by that stallion's son Pioneerof the Nile. Both Empire Maker and Pioneerof the Nile are formidable classic influences from the line of Unbridled. The 1990 Kentucky Derby and Breeders' Cup Classic winner, Unbridled has sired a winner of each of the Triple Crown races: 1996 Derby winner Grindstone, 2000 Preakness winner Red Bullet, and 2003 Belmont winner Empire Maker. Grindstone sired 2004 Belmont winner Birdstone, in turn the sire of 2009 Derby winner Mine That Bird and Belmont winner Summer Bird. Empire Maker's branch of the line has flourished recently. Pioneerof the Nile is the sire of 2015 Triple Crown hero American Pharoah, in addition to 2017 Preakness runner-up Classic Empire and 2014 Preakness third Social Inclusion. Empire Maker's son Bodemeister, runner-up in the 2012 Derby, sired 2017 Derby winner Always Dreaming in his first crop. Further helping Messier along on the pedigree front, he is out of a mare by stamina influence Smart Strike, whose sons and grandsons include Curlin, Lookin At Lucky, Exaggerator, Palace Malice, and Country House. Messier’s dam, Checkered Past, was a stakes performer on both turf and synthetic, and it is often borne out that horses with turf-type pedigrees often take well to the main track at Churchill Downs, particularly when it is wet. Consider the Derby victories by Barbaro and Animal Kingdom, both previously winners on the turf, and the third-place finishes of Dullahan, a synthetic stakes winner, and Paddy O’Prado, a subsequent turf Grade 1 winner. Paddy O’Prado’s performance came on a sloppy, sealed track. A.P. Indy, winner of the 1992 Belmont and Classic, has typically imparted his own stamina, as seen in the likes of his daughter Rags to Riches, winner of the 2007 Kentucky Oaks and Belmont Stakes; grandson Orb, winner of the 2013 Derby; and great-grandson California Chrome, winner of the 2014 Derby and Preakness. One of the best fonts of his stamina has been grandson Tapit, a perennial leading sire. He is the most successful sire in the modern history of the Belmont Stakes with four winners - Tonalist (2014), Creator (2016), Tapwrit (2017), and Essential Quality (2021). Tapit is also the sire of Frosted, Divining Rod, Hofburg, Lani, and Tacitus, all on the board in Triple Crown races. Tapit is represented in this Derby by Charge It, while Tapit’s son Race Day is the sire of Barber Road and White Abarrio. Charge It is also from one of the most stamina-laden female families in this year’s Derby. His dam is a daughter of multiple route Grade 1 winner and Broodmare of the Year Take Charge Lady, and she and her daughters are responsible for champions Will Take Charge and Take Charge Brandi and Grade 1 winners As Time Goes By, Omaha Beach, and Take Charge Indy. :: Get Derby Clocker Reports from Mike Welsch and the DRF Clocker Team to access exclusive insights from the morning workouts Blue Grass Stakes winner Zandon, the Derby's morning-line favorite, is by A.P. Indy's grandson Upstart. Zandon is also from a female family that has produced turf graded stakes winners Cairo Memories and Significant Form. Turf breeding could also move up the likes of Tiz the Bomb and Summer Is Tomorrow, both by sons of the versatile classic sire War Front, popular internationally for his turf performers. Candy Ride hails from another branch of the sireline responsible for Unbridled. The Mr. Prospector horse Fappiano, Unbridled's sire, is also Candy Ride's great-grandsire. Candy Ride's best son, Horse of the Year and record-setting freshman sire Gun Runner is represented by two major prep winners for his first Derby in Cyberknife and Taiba.  Not to be forgotten, Louisiana Derby winner Epicenter, the second choice on the morning line, is from the red-hot sire Not This Time, a son of late European Horse of the Year Giant’s Causeway. Giant’s Causeway, represented from his final crop by Classic Causeway, is generally regarded as a source of stamina. The average winning distance of his progeny is more than a mile, an outstanding figure as these numbers often skew downward due to a preponderance of sprint races in North America. A.P. Indy also falls into this category. Giant’s Causeway is by the late, great Storm Cat, whose line has had a strong recent run in the Derby. Authentic and Mandaloun are by leading sire Into Mischief, a great-grandson of Storm Cat; Medina Spirit was sired by Giant’s Causeway’s son Protonico; and Triple Crown winner Justify is a great-great grandson of the prolific sire. :: Kentucky Derby Headquarters: Get the latest news, info on contenders, past performances, picks, and more  Epicenter, as well as fellow Derby entrant Simplification, are actually bred on a similar pedigree pattern to Gun Runner. That champion is by Candy Ride out of a Giant’s Causeway mare. Both Epicenter and Simplification are by a son of Giant’s Causeway out of Candy Ride mares. The obvious outcross in this field is Japanese-bred Crown Pride, but he has international classic influences throughout his pedigree. His sire, Reach the Crown, was Grade 1-placed at 12 furlongs; his grandsire, Special Week, won at up to two miles; and his great-grandson is Sunday Silence, the 1989 Kentucky Derby, Preakness, and Breeders’ Cup Classic winner who went on to become a breed-shaping sire in Japan. Broodmare sire King Kamehameha, winner of the Japanese Derby, was another influential sire in his home country. He, in turn, is by French classic winner Kingmambo, classic sire in the U.S. of Lemon Drop Kid.