The commercial pecan (Carya illinoinensis) is native to North America, where it is an important species in riparian woodland ecosystems. The name illinoiensis indicates that the Mississippi River Valley in Illinois is the northernmost reach of its naturalized range. Pecans are native west of the Mississippi, particularly in Texas, Louisiana and Oklahoma, but Native Americans introduced them to a wider area.
The family Juglandaceae includes walnut, hickory and pecan, whose ancestors are well represented in fossil records of the Paleogene, at the beginning of the Tertiary, 65 million years ago. Dinosaurs were extinct. Juglandaceae diversified toward modern genera in mutual co-evolution with emerging small mammals and jays, which shaped a new strategy of seed dispersal. Pecans adapted to harvest by hoarders, who did not always re-harvest and consume all of their buried cache. Squirrels arose in North America 36 million years ago and influenced the pecan genus. Identifiable fossil Carya date to 34 million years ago.
Modern pecan species date only from the Pleistocene glacial period 1,640,000 to 10,000 years ago. As climate changed, older pecans became extinct in Europe and western North America. The modern pecan is a lowland riverine species and appears to have originated in the Red River Valley at the Texas-Oklahoma border and into Louisiana, where pecans exhibit the greatest genetic diversity. Pecan is a component of native forest stands throughout the lower Mississippi basin.
In the 1970s, archaeologists excavated Bakers Cave along the Pecos River near Del Rio, Texas. The site includes levels as early as 11,000 years ago. Pecan remains were found in levels from 8,000 to 5,000 years ago. A fossil modern pecan found in Mississippi floodplain sediment at Muscatine, Iowa dates to 7,280 years ago. Pecan peaks in the pollen record for the Upper Mississippi Valley correspond to the "Dalton artifact assembly," a complex of Paleo-Indian stone implements, about 10,000 years ago. Thus, human dispersal is assumed to have expanded the pecan's range.
In 1533, Cabeza de Vaca was shipwrecked on the Texas coast and later described Native Texans harvesting pecans along the Guadalupe River. About the same time, Hernando de Soto observed pressed pecan oil in southern Illinois. By the late 1600s, Native Americans living near San Angelo, Texas, routinely traded pecans into Mexico. By 1762, Creoles in New Orleans invented pecan pralines. The oldest surviving trees at Mount Vernon are pecans Thomas Jefferson gave George Washington as a gift.
In 1846, an enslaved gardener named Antoine created "Centenial," the first commercial pecan cultivar, by grafting 16 domesticated pecans onto wild rootstock at Oak Alley Plantation, near New Orleans. There are now more than 1,000 varieties of pecans grown on 19,900 U.S. farms in 24 states. Pecans traveled into space in the 1970s as the only fresh food for astronauts on the Apollo 13 and Apollo 14 moon missions.