In Eclipse, by Stephane Meyer, Jasper became a vampire during the Civil War. He was a soldier in Texas and fell on the battlefield. He was turned by a woman who wanted to build her own vampiric army to take territory from others vampires in the region. He helped her to do this, rising to a leadership position. Then, one day when he was given orders to kill the newborns because they were no longer useful or controlable, Jasper found himself unable to do so. He learned of a group of vampires living in the North who were not living as they were in the Southwest. This was when he found the Cullens and met Alice.
