Samuel Winchester was born to Mary Campbell Winchester and John Winchester on May 2, 1983. He was the second born of two, his brother Dean being four years older. The Winchesters lived a happy life in Lawrence, Kansas, until November 2, 1983 when Sam's mother was killed by the Yellow Eyed Demon, by being pinned to the ceiling above his crib, gutted, and engulfed in flames.
John and Dean rescued little Sammy from the burning house, and then left Kansas. To go on the road. And hunt down the demon that killed Mary Winchester.
The boys grew up on the road, and Sam was basically raised by his brother Dean from a very young age as their father was often out hunting and left them alone for weeks on end sometimes. When he was old enough to start school, Sammy and Dean both went to what ever school was in the are of the hunt their father was on. And while their father used assumed names, the children always used their real names when enrolling in school. They just never stayed very long.
As Sam grew up, he became an extremely inquisitive child, wanting to know how his mother was killed, but always too afraid of his father to ask, so he asked his brother Dean one Christmas and he told him. Their mother was killed, monsters were real, and dad went off to hunt them. From that point on Sam thought his father was kind of like a super hero.
But that changed as he grew up. John Winchester, who was retired military, raised his sons like little warriors, training them for the hunt and the fight.
When Sam was old enough to go to College, he did. After a huge blowout fight with his father, which was the escalation of the tension that had grown between the two of them, Sam informed his father and brother that he was going to Stanford.
John's reaction was to tell him to get gone and don't come back. So he did.
Sam put his life of hunting the supernatural behind him until Halloween night during his senior year. He and his girlfriend Jessica and their friends had gone to a Halloween party and Sam was nervous about an interview for law school. Sam really didn't…DO…halloween, but would never explain why.
That night, while sleeping, his training dormant, but not forgotten, he awoke to the sounds of a possible intruder. In the dark he and the intruder fight, and he pins them, only to be looking down at the face of his brother Dean.
Dean informs Sam, that their father is on a "hunting trip" and hasn't been home in weeks. Reluctantly Sam goes with his brother to find their dad. They come across a Lady in White while searching for John, and hunt the ghost down, saving the lives on innocent men. According to their bargain, Dean drops Sam back off at Stanford and as he lays down on his bed, happy to be home he feels drops of blood hit him in the forehead. Looking up, his girlfriend Jess is pinned to the ceiling, exactly like his mother and is engulfed in flames. Dean comes bursting through the door and saves Sam once again, and Sam agrees to find Dad, and go and try to kill the Yellow Eyed Demon once and for all.
Throughout the next couple of years, Sam and Dean, using their dad's hunting journal as guide and roadmap, hunt down all manner of evil and kill it, saving people all over the U.S. They live off scam money and forged credit cards, narrowly escaping the police and the feds (and sometimes getting caught).
When Sam turns 22 he starts getting psychic visions about people who are going to die. They investigate, reunite with John who has been off hunting the demon that killed his wife, and they learn that Sam has several drops of demon blood in him. Azazel, aka the Yellow Eyed Demon, had dropped some blood in his mouth (as he had with several other special children) when he was six months old, and that Mary had tried to stop him and was killed because of it.
The Winchester go after Azazel, fight him, and lose. As Sam is driving them all to the hospital their car is rammed by a big rig and they are taken to the hospital.
Dean is in a coma and both John and Sam are battered and bruised but fine. John makes a deal with Azazel to trade his life and hand over a special gun built by Samuel Colt that can kill demons, so that Dean can live. Sam and Dean then go off and try to kill the demon that has now taken BOTH parents.
They hunt the demon down, and Sam ends up in a ghost town with other "sepcial" children of Azazel's. The one who ends up alive at the end of this little "game" is going to be Azazel's right hand man in a war that is coming. Jake and Sam are the only two left and Jake stabs Sam in the back with a knife moments before Dean, and their life long friend and hunter Bobby Singer, can get to him.
Dean cannot handle Sam's death and summons a crossroads demon to make a deal for Sam's life. He's given one year in exchange for Sam. A really shitty deal.
Sam, Dean and Bobby go to find Jake and stop him from opening a Devil's Gate – a gate to hell – with the help of an old hunter's wife named Ellen Harvelle. They are unable to stop the opening of the Devil's gate, but Sam kills Jake and Dean kills the Yellow Eyed Demon with a little help from the ghostly John Winchester.
They live out the next year hunting and doing everything in their power to find out how to save Dean from going to hell.
Along the way, the meet Ruby a demon who wants to help them and guide them to the ultimate mission of killing a demon named Lilith, who is the holder of the contract for Dean's soul.
At the end of Dean's last year, they meet up with Lilith but are unable to stop her and they have not been able to find a way out of Dean's deal. Sam even tried killing the crossroads demon Dean made the deal with. It was no use.
Lilith orders a hell hound to kill Dean and tries to kill Sam, but her powers do not work on Sam at all. She flees, sending Ruby back to hell. Dean has been made dog food by a hell hound and Bobby and Sam must burry Dean Winchester.
After they burry Dean, Sam starts drinking heavily and sets about trying to find and kill Lilith – or get killed by her – one or the other. Ruby shows up, and tries to stop him from doing something stupid. She also convinces him to start using his psychic powers to vanquish demons now that Dean is gone.