In the summer of 1971, the world’s best women’s soccer teams competed in Mexico. Copa 71 still ranks as the best attended women’s sporting event of all time. So why do we never hear about it? Copa 71 tells the incredible story of the tournament that was written out of sporting history.

The opposition to women’s soccer goes back a long way. Many soccer associations even banned women’s teams. After the success of the men’s World Cup in 1970, the Mexican business community proposed holding a women’s tournament the following year. This purely commercial venture, which was not supported by FIFA, proved to be a resounding success. Soccer-crazy Mexico embraced the tournament, and the country’s two largest stadiums were filled. Copa 71 could have been the launch of women’s soccer worldwide. But the male-dominated establishment wasn’t ready for that.

Half a century later, the women who played in the tournament still find their experiences unbelievable. Ordinary girls, mostly from simple backgrounds, were welcomed as heroes in Mexico. It was “like a parallel universe,” as one of them put it.