The most accepted origin of the story as far as New Jerseyans are concerned started with Mother Leeds and is as follows:
"It was said that Mother Leeds had 12 children and, after giving birth to her 12th child, stated that if she had another, it would be the Devil. In 1735, Mother Leeds was in labor on a stormy night. Gathered around her were her friends. Mother Leeds was supposedly a witch and the child's father was the Devil himself. The child was born normal, but then changed form. It changed from a normal baby to a creature with hooves, a horse's head, bat wings and a forked tail. It growled and screamed, then killed the midwife before flying up the chimney. It circled the villages and headed toward the pines. In 1740 a clergy exorcised the demon for 100 years and it wasn't seen again until 1890."
"Mother Leeds" has been identified by some as Deborah Leeds. This identification may have gained credence from the fact that Deborah Leeds' husband, Japhet Leeds, named twelve children in the will he wrote in 1736, which is compatible with the legend of the Jersey Devil being the thirteenth child born by Mother Leeds. Deborah and Japhet Leeds also lived in the Leeds Point section of what is now Atlantic County, New Jersey, which is the area commonly said to be the location of the Jersey Devil story.
Reportedly in 1778,Commodore Stephen Decatur visited the Hanover Iron Works in the Barrens to test cannonballs at a firing range, where he allegedly witnessed a strange, pale white creature winging overhead. Using cannon fire, Decatur purportedly punctured the wing membrane of the creature, which continued flying – apparently unfazed – to the amazement of onlookers.
Additional legend puts this encounter at 1819 and at the behest of President James Monroe. Work on Decatur's House in DC from 2007 -2008 has led to speculation that his Jersey Devil sighting was more than mere chance. Decatur was definitely in New Jersey testing the quality of cannonballs produced by Batsto and Hanover. Included in his entourage was Dr. James Killian, famed abnormalist and cryptid hunter from the 19th century. Legends throughout New Jersey and Southeastern Pennsylvania have these two men in scientific pursuit of the animal.
A bizarre rotting corpse vaguely matching the Jersey Devil description was discovered in 1957, leaving some to believe the creature was dead. However, there have been many sightings since that time.
On January 23, 2008 the Jersey Devil was spotted again this time in Litchfield, Pennsylvania by a local resident that claims to have seen the creature come barreling out of the roof of his barn.