This week, the film The Most Hated Woman in America comes to Netflix, with Melissa Leo playing Madalyn Murray O’Hair, the atheist who campaigned against the church’s influence in public and political life (the title comes from the headline on a 1964 interview with her in Life magazine). While Murray O’Hair is not widely known outside of the US, she had an extraordinary life. Long before the likes of Richard Dawkins, she gained notoriety for helping to push bible readings out of schools, and in 1963 she founded American Atheists. It’s a group that is still going today, campaigning against Donald Trump’s plan to abolish the rule that forbids religious institutions, among other charitable organisations, from getting involved in political activity and funding). For the next few decades, Murray O’Hair devoted her life to campaigning against the church’s power. She was a contentious figure, and when she disappeared in 1995, along with her son and granddaughter from their home in Austin, Texas, that too was controversial.

People wondered whether there could be a sinister explanation. With still no sign of the family eight months on, a piece in the New York Times suggested that there were “two widely discussed explanations about the disappearances”. The first was that the trio had gone on the run with money they’d embezzled from the organisation. “The other,” they reported, “is that Mrs O’Hair, 77, diabetic and in declining health, was taking action on her desire to die without others praying over her corpse.”

Neither proved to be true: in 2001, their bodies were found, dismembered and hidden on a ranch in Texas, not murdered by one of the many enemies Murray O’Hair had made (death threats were common and she had been physically attacked), but by a former employee at American Atheists and two accomplices. It was a horrific end for one of the most interesting women of the second half of the 20th century.

In life, Murray O’Hair was funny, foul-mouthed and abrasive; she once said her favourite pastime was “thinking and beer drinking”. She described herself as a “militant feminist” (in, ironically, an interview with Playboy; she also wrote articles for pornographer Larry Flynt’s Hustler magazine, and wrote speeches for his presidential bid). She went on to call herself “an anarchist … and an integrationist and an internationalist – and all the other ‘ists’ that people seem to find so horrible these days. I embrace all of them.” She wasn’t a communist, although she was regularly accused of being one. Her response? She named her dogs Marx and Engels.

Later, she was criticised for being a self-publicist, money-hungry, and was disowned by her older son who became an evangelical Christian. But, although her fame dwindled, her victories were lasting. The requirement for prayers in schools had been ended in 1962 after a supreme court decision, but the following year another case Murray O’Hair was involved in led the supreme court to rule that bible readings were unconstitutional. In God-fearing America in the 1960s, this was a big deal (in schools in the UK, there is still a requirement for daily “collective worship” which should be “wholly or mainly of a broadly Christian character”). The landmark ruling made her famous, and she regularly appeared on TV and the radio, pushing her subsequent campaigns, which included attempting to sue the pope and trying to get the words “In God we Trust” removed from US currency.

She was ridiculed, dismissed as a crank and then largely forgotten about, but she often talked sense. “There’s an absolute steady retreat,” she said in an interview in 1989, “into what I call neofascism – but it’s really old-time fascism – into a robber-baron society and a religiously dominated society, and that’s not cyclical because they have new weapons at hand now, mainly communications technology with which they can rapidly disperse ideas.” You might call Madalyn Murray O’Hair prophetic, if that wasn’t a word she would have hated.

The Most Hated Woman In America is available on Netflix from 24 Mar