When AMC began assembling the cast for its first original series, Mad Men, creator Matt Weiner was adamant that he wanted to cast mostly unknown actors, so that they wouldn't bring the "baggage" from previous roles to the new project. This way, the audience would come to the characters with fresh eyes.

What resulted was a series of gambles by the network, which assembled a group of actors, many of whom had never been on the set of a television show before. To coincide with the 10th anniversary of the pilot, which premiered on July 19, 2007, here are the stories of how the characters we know and love today were born.

Check out our full oral history of the Mad Men pilot here!

Jon Hamm (Don Draper)

Looking back, it seems impossible that anyone besides Jon Hamm would have been able to play Sterling Cooper's handsome, brooding creative director, Don Draper. But in actuality, it was anything but inevitable, with everyone involved in the show realizing that the choice for the lead actor could make or break the project.

"It was torturous finding Don Draper," Alan Taylor, who directed the pilot, admits. "It was all going to stand or fall based on Don."

Hamm was put through a grueling audition process that required him to come in, by his own estimation, seven to eight times, including once for an 8 a.m. read in the middle of a rainstorm, as well as a whirlwind trip to New York to meet with skeptical AMC executives.

"It was one of those things where, you're only as good as your last audition, and it just takes one bad one to kind of mess it all up," Hamm recalls. "I was just hoping I wasn't going to have a bad audition."

The casting directors and creator Matt Weiner fell in love with the unknown actor immediately, but the AMC executives took a little more convincing.

"We felt like we hit the jackpot when we met Jon," according to casting director Kim Miscia.

But AMC's senior vice president of original programming, Christina Wayne, watched Hamm's audition on tape rather than in person and had a different view. "Matt originally sent us tapes on Jon Hamm and Mariska Hargitay's husband [Peter Hermann]. Those were his two choices and he said he was leaning more towards Jon," she recalls. "We were like, 'Really? This is the guy you want?' It was not a particularly great audition."

Taylor, who had previously worked with Weiner on The Sopranos, also wasn't immediately sold on Hamm, but for different reasons.

"My theory, looking back, was that we had come off Sopranos and had this antihero, not classically handsome leading man. And I had gotten into the habit of thinking, OK, that's what it takes to do a serious show. It's not just pretty boys. So I think I had a reluctance about Jon's handsomeness," he says. "It was only after we started to work with him and see that there was a kind of sadness and vulnerability ... that I started seeing that side of him. What [Mad Men] was doing was sort of dismantling masculine perfection and letting it fall apart. So it made perfect sense to start off with someone who seems from the outside to be that perfect American male. But it took me a while to catch up to that."

Hamm eventually flew to New York and went to a meeting with Wayne, Taylor and other AMC executives to secure the role.

"Matt was telling us he just knew it in his gut and he could see it," Wayne says. "So, I made the decision to fly Jon Hamm from L.A. to New York to meet with me in person. [We] took him for a drink, and it was immediately apparent in person that he would embody Don Draper. ... I think that just shows the genius of Matt, that he knew. All of us were still floundering around, and he knew what he wanted and he was 100 percent right."

See exclusive behind-the-scenes photos from the Mad Men pilot

Elisabeth Moss (Peggy Olson)

Elisabeth Moss was the first person to read for fresh-out-of-school secretary Peggy Olson, and the casting directors — who had known her since she was a child actress — knew they had found their woman. "She blew everyone away, but as the casting process goes, you can't just see the one person," Bowling says. "But that's always stuck with me, how amazing it is that the first person who came in to read Peggy ended up getting the role."

At 23, Moss was younger than many of her co-stars, but was one of the few cast members who had prior experience working in television, thanks to her role as First Daughter Zoey Bartlet on The West Wing. That, combined with the fact that some of her co-stars were tasked with being despicable to her (in character) on Day 1, made for an interesting dynamic as the new colleagues were getting to know each other.

"There's a status, whether it's explicit or implied, on a set, based on experience," co-star Rich Sommer says. "If you're on a set with Brad Pitt, you're generally going to defer to him. We didn't have a Brad Pitt, but we had really inexperienced people like me and Aaron and Michael, and then you had more experienced people like [John] Slattery and Lizzie and [Jon] Hamm. I just sort of steered clear of her because I didn't want to mess with her, but she seemed nice."

Christina Hendricks (Joan Holloway)

Hendricks first landed an audition for the role of Peggy, Don's new secretary, and recalled thinking, "This is ridiculous." The casting office agreed with her, and she was asked to read for the role of office manager Joan Holloway, then for Don's mistress Midge, and then for Joan again. The casting directors zeroed in on Hendricks for the role of Joan, but Hendricks herself didn't have a preference. "I said, 'I don't care what character it is. All the roles were good, so whichever one is the series regular is the one I want.'"

But it almost never happened. Like many of the other characters, Joan was originally conceived as a guest-star role who would be promoted to a series regular if the show got picked up. And in the meantime, Hendricks had also gotten an offer for another pilot. "I had to make this decision to either be a guest star on Mad Men or test on this other show, and I just loved it so much, it was like, I'll do Mad Men," Hendricks says.

January Jones, <em>Mad Men</em>January Jones, Mad Men

January Jones (Betty Draper)

At the advice of her manager, who believed the role of Don Draper's wife Betty would be insignificant due to her minimal presence of the pilot, January Jones also originally auditioned for the role of Peggy — which threw everyone involved with the casting process for a loop.

"I had always thought she should play Betty, because I saw her as this Grace Kelly Stepford wife type. Super beautiful and super icy cold," recalls Christina Wayne, who knew Jones and called her manager to encourage her to audition. "He sent her in for Peggy and Matt [Weiner] was like, 'What the hell was that?'"

But Jones and her team were still unsure about the character of Betty because there was so little material for them to go on, so Weiner wrote a couple of additional scenes for Jones to audition with.

"Matt Weiner said, 'Listen, there's this tiny role at the very, very end of the wife.' And I immediately was like, 'But she doesn't do or say anything. Of course I will read for the wife, but there's nothing to say,'" Jones recalls. "He said, 'Well, come back in.' It was either the next day or two days later, and he had written two scenes, like, overnight for her, so that I had something to audition. And both those scenes ended up in Season 1."

For the people involved in the project, the fact that Weiner could come up with meaningful material at essentially a moment's notice was yet another indication of how much thought he had already put into the show and its characters.

"In the middle of prep for this pilot, he went home and wrote a scene," marvels Miscia. "And it was the most beautiful scene, too. I was so floored by his talent, that he was able to turn that around with everything else he had going on."

John Slattery (Roger Sterling)

John Slattery, who was known to the casting office for his stage work in New York, was one of the first actors to be cast in the show as Don Draper's boss, firm partner Roger Sterling. However, the actor came to the role in a semi-roundabout way, after being asked to come in to read for the character of Don.

"The part of Roger wasn't as much in evidence in the pilot, so they tricked me by saying they wanted me to read for [Don's] part. ... And then they said, 'How about this guy [instead]?'" Slattery told Anderson Cooper in 2012. "I took it on faith basically. Matt Weiner said it would be a great part, and it [was]."

Vincent Kartheiser (Pete Campbell)

For the role of Pete Campbell, Weiner knew he wanted someone a little more "boyish" to set up as the irritating potential rival for the more manly, and senior, Don Draper. But Kartheiser almost blew his chances.

"We knew what Vincent was capable of," Miscia recalls. "When he came in the first time in Los Angeles, he was under the weather with unwashed hair and like a sweatshirt. He wasn't off-book. And Matt looked at me like, 'Are you insane?' I was like, 'No, I promise! He's the guy!' I had to call his agent back and tell him to take a bath, and then he came in and delivered the winning audition."

Rosemarie DeWitt (Midge Daniels)

DeWitt was another no-contest choice for Midge, Don's bohemian downtown mistress. "She was always just heads and shoulders above the next choice," Miscia remembers.

Michael Gladis (Paul Kinsey)

Gladis' caught the eye of Matt Weiner and Alan Taylor thanks to his resemblance to another, more legendary, actor. "They remarked on how much I looked like Orson Welles. I told them that I had actually been cast in a film about the young Orson Welles that fell apart and that it broke my heart," Gladis says. "Later on, I [heard] when Alan and Matt were talking about who to cast, they said, 'Oh, we've got to get the Orson Welles guy in there.'"

Gladis would go on to play Paul Kinsey, but his name in the pilot — though it's never spoken — was "Dick." That changed when the show was picked up to series and Weiner wanted to use the name "Dick" for Dick Whitman, Don Draper's true identity. But, like his co-stars Rich Sommer, Aaron Staton and Bryan Batt, Gladis had only signed on for a guest role in the pilot, so he had to go back in and re-audition for the series regular role of "Paul Kinsey."

"They wrote the role Paul Kinsey and thought, which of the guys that we already hired do we think would be good for this role?" Gladis remembers. "I'd moved to L.A. for, like, the job of my life, and I get a call from my manager saying, 'This is sort of strange, but they just sent us eight pages of sides, and they'd like you to go in and read for Matt and [producer] Scott [Hornbacher] and Alan for this new role that they think you can play. You'll be part of the show no matter what, but they want to see if you can play this role.' It was crazy."

Rich Sommer (Harry Crane)

Sommer originally auditioned for the role of "Dick," who later became Paul Kinsey, but was offered the role of Harry Crane after another actor turned it down to focus on a play. "At the callback I accidentally called Matt Weiner 'Alan' and called Alan Taylor 'Matt.' And I was like, well, that just completely seals the deal. Let's just move on with our lives," Sommer recalls. "I heard that I had gotten the job differently than other people did, because I was not first choice for Harry Crane. ... They called me about two hours before the table read and said, 'Congrats, you got it. Can you be here in two hours? And I said, 'Yep. I'm super unemployed, so I will be there."

Like his counterparts Dick-slash-Paul Kinsey and Ken Cosgrove, Harry Crane is not named in the pilot and Sommer knew nothing about the character — which was deemed a guest role — going in. "During the pilot we were sort of described as this Greek chorus. We were effectively interchangeable, except that one of us wore glasses," Sommer says. "From the second episode on, those characters instantly start becoming more defined. I think it's the second or third episode you find out that Pete and Harry knew each other back in college. You immediately find out Harry's married and flirts but doesn't cheat. You find out that Paul is sort of a bohemian weirdo who smokes a pipe and wears sweaters and talks about Star Trek all the time. But those clarifications didn't really come out until the show started in earnest. There wasn't really time for it in the pilot. There were bigger fish to fry."

Kristen Schaal (Nanette)

Here's a bit of Mad Men trivia for you: Kristen Schaal, who would go on to star on 30 Rock and The Last Man on Earth, was thisclose to getting her big break in 2005 when she was cast in the Mad Men pilot as Nanette, one of the telephone operators at Sterling Cooper. The original intent was that the operators would continue to appear in the series if it was picked up, but they are not seen beyond the pilot.

"I was really excited about casting Kristen Schaal in one of those roles, because she was so quirky and hard to cast at that time, and so talented," Miscia recalls. "I thought, oh my gosh, this is the perfect role for her. And then, those girls didn't really end up going to series like the original plan was."

Bryan Batt (Sal Romano)

Batt's casting as art director Sal Romano was a happy accident. After the casting office approached him to read for the role, Batt turned down the offer because he had booked a surprise trip to Paris as a thank-you to his godchild, who had quite literally saved the day for the part-time Louisiana resident when Hurricane Katrina hit in 2005.

"My partner and I have a business in New Orleans, and we were out of town when Katrina hit," he explains. "My godchild was able to board up our house, raise everything up, board up the store, the business. Drove my mother out of town. And also, she borrowed our car to do so. So she saved the car, the store, the house, and my mother. My audition for Mad Men came up exactly the week we were in Paris. So for the first time in my life, I didn't even question. I chose life over show business."

Several weeks later, while in New York rehearsing for an off-Broadway play, Batt got a call that the casting process was still happening, and he went to audition on his lunch break. The rest, as they say, is history.

Aaron Staton (Ken Cosgrove)

Staton originally auditioned for the role of Pete Campbell. "I didn't get the role, obviously, but I got a call, like, 'Hey, do you want to play this smaller role in the pilot?'" Staton recalls. "That was the beginning of the next 10 years for me."

But the part was just for a guest role in the pilot, and Staton was pleasantly surprised to learn that he would be joining the cast full-time when the series was picked up.

"Aaron had, like, four lines to audition with, and he became a series regular," Miscia recalls. "That would never happen in today's world of television."

Maggie Siff (Rachel Menken)

For many of the actors, including Siff (who was fresh out of school), the audition for Mad Men came at the end of a particularly dismaying pilot season. "It had just been this horrible winter of trudging through Midtown going on one terrible television audition after another," Siff recalls. "I remember reading the script and loving it so much. It felt so qualitatively different from anything. It almost felt like an art project."

Like many of the actresses, Siff originally responded to the role of Peggy, but then she and her manager decided on the morning of audition that she should read for the part of Rachel Menken, the Jewish department store owner who clashes with Don in the boardroom (and goes on to become his love interest).

"Having a confidence about a role is a very rare thing, and there was just something about the script and the character and my conviction about it that I've only ever felt a couple of times," Siff said. "For some reason, I left every audition feeling like, no, I actually might be the best person for that job. and I don't know why. I just really carried that with me through the whole process."

And it was a process. Casting the character of Rachel Menken sparked "spirited debates" among the casting directors and Weiner. But Siff knew she was destined to be a part of the show.

"My manager after a while was like, 'Well, this isn't a good sign.' He was like, 'If he can't make up his mind, that usually means it doesn't go your way,'" she recalls. "And I was like, 'No, I'm getting this job.' I just knew that I was getting the job. I was like, 'They can call me back as much as they want. I'm getting the job.'"