"I have a powerful mother, I have two professional older sisters, I have a professional, powerful wife, and there have always been a lot of women in authority on the show," Weiner says. "My mother was what they called a women's libber. I knew who Betty Friedan was, I knew who Gloria Steinem was, I knew who Bella Abzug was, I knew who Simone de Beauvoir was, and then intellectually in college, feminism was the most prominent idea."

When Weiner was fleshing out the universe years ago, two books, which he read in the course of a single week, were particularly instructive: by Friedan and by Helen Gurley Brown. "I thought: 'Well, a lot has changed', but not a lot has changed," he recalls.

Contrary to other popular entertainment about the 1960s, focuses not on activists or hippies but on members of Richard Nixon's "silent majority". Its characters, by and large, are not the type to sit in at lunch counters or burn their draft cards. Instead, they craft advertising campaigns for companies that make napalm and refuse to hire black employees.

Likewise, there is a big difference between being a feminist show and being a show about feminists. has always resisted becoming the latter, reluctant to use its women as emblems of any particular movement. Peggy and Joan are unwitting trailblazers, compelled to break barriers by circumstance as much as ideology, and the era's suffocating gender expectations aren't the only - or even the main - thing keeping Betty from finding happiness. Still, the series left off in summer 1969, and the year ahead marked a pivotal time for second-wave feminism: Abzug was elected to Congress, and the influential books by Kate Millett and by Germaine Greer were published.

While 's track record suggests it's unlikely that any of these characters will be forming consciousness-raising groups in the seven episodes that remain, "they are all starting to have a different voice than they had", Weiner says. "They're starting to be heard."

In the pilot episode, Peggy Olson (played by Elisabeth Moss), a naive 20-year-old from Bay Ridge, Brooklyn, by way of Miss Deaver's Secretarial School, arrives for her first day of work at Sterling Cooper, a Manhattan advertising agency, and is assigned to work for creative executive Don Draper.

She quakes in fear around the poised office manager, Joan Holloway, and is such an outer-borough bumpkin that account executive Pete Campbell wonders if she might be Amish. Nevertheless, there are hints that Peggy may be more formidable than she appears: when Don, hung over and waking from a nap, asks her to go out to entertain Pete, she politely but firmly says: "I don't want to seem uncooperative, but do I have to?"

Since then, Peggy has grown to become Don's protegée, his rival and for a time his de facto boss. She also bought a brownstone and gave a baby up for adoption. The similarities between Don and Peggy have been widely noted - both are passionate about their work and have painful secrets in their past - but unlike Don, whose very identity is a lie, Peggy has a guilelessness that makes her an accidental feminist.

"She just keeps bumping her head up against this glass ceiling, not even recognising that it's there," Moss says.

Weiner says he has always envisaged as the "parallel stories of Don Draper and Peggy Olson", though he realises now that it's "probably unusual in some way that I thought about what Peggy wanted". It took longer for Moss, who has received five Emmy nominations for , to realise how integral Peggy's journey has been to the series.

"It was really only in the third or fourth season when I heard other people saying things about her place in the show," the actress says. "I said: 'Oh, no, no. It's Don Draper's story.' There's still a huge part of me that believes that."

Joan Harris (Christina Hendricks) is the embodiment of the Steinem quote: "We are becoming the men we wanted to marry."

At the dawn of , Joan was a career girl in the Helen Gurley Brown mold, in command of her sexuality and fully aware of how to use her looks to advantage. Though she was dazzlingly proficient at her job as office manager and liberated enough to know a doctor willing to prescribe the pill to unmarried women, she had what Weiner describes as "Stone Age expectations". As she tells Peggy on her first day: "If you really make the right moves, you'll be out in the country and you won't be going to work at all."

That is, until her disastrous union with Greg, a handsome doctor who once raped her and fled to Vietnam when he failed to receive a surgical residency. As her marriage was unravelling, Joan became pregnant after a desperate assignation with former lover Roger Sterling and decided to keep the baby.

Joan is a heartbreaking mix of confidence and vulnerability. Though she almost single-handedly keeps the office running, she, unlike Peggy, is reluctant to seize opportunities not traditionally allotted to women.

After seven seasons, January Jones has had it with the Betty hate. "I'm sick of defending her and the things she's not good at or the mistakes she's made," says the actress, sporting a very un-Betty-like lavender streak in her hair during the series' press blitz in New York.

It's little wonder Jones is over it: Betty has been subjected to greater criticism than perhaps any other character on - including Don, her alcoholic, identity-stealing philanderer of an ex-husband. "She was very flawed, complicated and emotionally immature," Jones says. "But I miss speaking for her. She made me brave."

Detractors most often cite Betty's shortcomings as a parent, but her problems stem from insecurity rather than a lack of love for her children. She shines when she feels needed, such as when Sally got her period for the first time.

For a long time, Betty's problem was Don. But her second husband, Henry, a state senator, is faithful, kind and emotionally available to both her and her children - "everything that Don wasn't", as Jones put it.

Betty is defined by her role as a wife and mother, but always craves more. So she shot the neighbour's pigeons, slept with a stranger in a bar, binged on Bugles and whipped cream, and dyed her hair.

The first time viewers really catch a glimpse of Sally Draper (played by Kiernan Shipka), she is wearing a plastic dry cleaning bag over her head. "If the clothes from that dry cleaning bag are on the floor of my closet, you're going to be a sorry young lady," Betty scolds her.

It was the first of many moments of physical and emotional peril for the eldest Draper child, who has endured a staggering amount of psychological trauma in her 15 years; adolescence is hard enough without walking in on your father in bed with his mistress. Though she's developed an unfortunate smoking habit and a sullen teenage eye roll, Sally is surprisingly well adjusted.

"She has the traits and the qualities and the work ethic and the determination and the strength of a hard worker," says Shipka, who has spent more than half her young life on but wasn't allowed to watch it until recently. "She has what it takes to be someone very important, I think."

After years of ups and downs, Sally's fraught relationship with Betty has reached a fragile detente. "Sally's never necessarily liked her mother, but she's always loved her. I think that kind of describes their relationship," Shipka says.

Sally's relationship with Don has likewise evolved in a promising direction. Even after the mistress faux pas, "she really sees him for who he is now", Shipka say.

Best of all, Sally can look forward to options that weren't available to Betty, Joan or even Peggy. "Sally is someone who will get to think about what she wants to be," Weiner says. She'll just have to worry about whether she can have it all … but let's save that for the spin-off.