Ellen Harvelle was married to Bill Harvelle, who was killed in a hunt. She owns a bar, Harvelle's Roadhouse, that her daughter Jo helps out at, as well as computer genius Ash.
"Working with him [Chad Lindberg] was an absolute scream. On my coverage, I would literally have to say, 'Chad, don't even be Ash, just say the words,' because I could never hold a straight face. He was the most fun of any character actor I've ever worked with, because he really owned it. He was a really lovable goof on the show." - Samantha FerrisSupernatural The Official Companion Season 2, p. 134
"The character was named Ellen because the initial impulse in the writer's room was to model her after the tough yet emotionally-vulnerable character Ellen Barkin often portrays."Supernatural The Official Companion Season 2, p. 14
The writers spent so much time with a father-son relationship dynamic, that they wanted to explore a mother-daughter dynamic, which is where Ellen and Jo came about.Supernatural The Official Companion Season 2, p. 14
Ellen was never to have a fling with John, only platonic. So why did John never tell the boys about the Roadhouse? That's when the backstory came about, where John killed Ellen's husband.Supernatural The Official Companion Season 2, p. 14-15 "My husband and I were very, very close to him. And, in the end, he's responsible for the death of my husband. So I'm worried about these boys' intentions. Jo wants to go demon hunting, and it's very dangerous. I don't want my daughter to be killed like my husband was. But I do end up loving the boys dearly, and I would protect them with my life." - Samantha FerrisSupernatural The Official Companion Season 2, p. 134
"Ellen brought a maternal energy for our world, which the boys have never had before, which I found was really interesting. Like a lioness, which is tough and badass and 'You touch my children, I will kill you.' Samantha Ferris really brought that character to life. She was everything you wanted the character to be - she was nuanced and complex and tough, yet beautiful and feminine." - Eric KripkeSupernatural The Official Companion Season 2, p. 15
As Samantha puts it, Ellen is "a gun-toting, beer-slinging, bar-owning broad. But there's a very maternal core inside her. Ellen has seen a lot in her life. She's not jaded, but she's guarded. And she's very protective of the things she has in her life, including her daughter, and the boys."Supernatural The Official Companion Season 2, p. 134