Who created the Hulk?

"There I was at my desk, a brand-new sheet of paper in my typewriter, ready to begin anew the agony of creation. What kind of hero was the comic-book reading world waiting for? What could we come up with that would take fandom by storm? How about an Errol Flynn type? Or a Gary Cooper? But then that little voice kept whispering inside my head, 'Be innovative. Be original. They expect you to come up with something that's different.'....
I had pretty much decided to let our second Marvel-style magazine feature someone with superhuman strength. But there had been, and still were, many such characters at that time, with National Comics' [DC's] Superman as the first that comes to mind. Certainly there would be nothing terribly original about someone who had the strength of Superman. But that's where the fun came in. It would be my job to take a cliche concept and make it seem new and fresh, exciting and relevant.
Once again I decided that Jack Kirby would be the artist to breathe life into our latest creation. He had already gained an enthusiastic coterie of fans with his interpretation of The Fantastic Four and was more than capable of doing an additional feature strip or two. So the next time we met I outlined the concept that I'd been toying with for weeks.
I've always had a soft spot in my heart for the Frankenstein monster. No one could ever convince me that he was the bad guy, the villain, or the menance. It was he who was sinned against by those who feared him, by those who first instinct was to strike out blindly at whatever they couldn't comprehend. He never wanted to hurt anyone; he merely groped his tortuous way through a second life trying to defend himself, trying to come to terms with those who sought to destroy him.
I suppose you can guess where we're heading. Think of the challenge it would be to make a hero out of a monster. We would have a protagonist with superhuman strength, but he wouldn't be all-wise, all-noble, all-infallible. (How's that for a rollicking redundancy?) We would use the concept of the Frankenstein monster, but update it. Our hero would be a scientist, transformed into a raging behemoth by a nucelar accident. And--since I was willing to borrow from Frankenstein, I decided I might as well borrow from Dr. Jekyll and Mr. Hyde as well--out protagonist would constantly change from his normal identity to his superhuman alter ego and back again."
from The Origins of Marvel Comics, Stan Lee, Simon and Schuster, 1974, pp. 74-5

"KIRBY: The Hulk I created when I saw a woman lift a car. Her baby was caught under the running board of this car. The little child was playing in the gutter and he was crawling from the gutter onto the sidewalk under the running board of this car -- he was playing in the gutter. His mother was horrified. She looked from the rear window of the car, and this woman in desperation lifted the rear end of the car. It suddenly came to me that in desperation we can all do that -- we can knock down walls, we can go berserk, which we do. You know what happens when we're in a rage -- you can tear a house down. I created a character who did all that and called him the Hulk. I inserted him in a lot of the stories I was doing.
Whatever the Hulk was at the beginning I got from that incident. A character to me can't be contrived. I don't like to contrive characters. They have to have an element of truth. This woman proved to me that the ordinary person in desperate circumstance can transcend himself and do things that he wouldn't ordinarily do. I've done it myself. I've bent steel.
GROTH: Was the child caught between the running board...
KIRBY: He wasn't caught. Hw was playing under the running board in the gutter. His head was sticking out, and then he decided he wanted to get back on the sidewalk again. But being under the car frightened his mother. He was having difficulty crawling out from under the running board, so his mother looked like she was going to scream, and she looked very desperate. She didn't scream, but she ran over to the car and, very determined, she lifted up the entire rear of that car. I'm not saying she was a slender woman. [Laughter] She was a short, firm, well-built woman -- and the Hulk was there. I didn't know what it was. It began to form.
ROZ KIRBY: You also said the Hulk reminded you of Frankenstein.
KIRBY: The Hulk was Frankenstein. Frankenstein can rip up the place, and the Hulk could never remember who he formerly was.
GROTH: Well, this is probably going to shock you, but Stan takes full credit for creating the Hulk. He's written, 'Actually, ideas have always been the easiest part of my various chores,' and then he went on to say that in creating The Hulk, It would be my job to take a cliched concept and make it seem new and fresh and exciting and relevant. Once again, I decided that Jack Kirby would be the artist to breathe life into our latest creation. So the next time we met, I outlined the concept I'd been toying with for weeks.'
KIRBY: Yes, he was always toying with concepts. On the contrary, it was I who brought the ideas to Stan. I brought the ideas to DC as well, and that's how business was done from the beginning.
GROTH: Stan also claimed he created the name, 'the Hulk.'
KIRBY: No, he didn't.
ROZ KIRBY: It's just his word against Stan's.