Ten years ago this month, “Brokeback Mountain” was released into movie theaters.

By all conventional box-office wisdom, the movie should have dropped like a stone, closed within a week and would have been but a footnote in film history.

What happened was far different.

The drama directed by Ang Lee and starring Heath Ledger and Jake Gyllenhaal as two shepherds who unexpectedly fall in love on a lonely Wyoming mountain in 1963 become a cultural flashpoint on the road to equality.

Its story of love denied resonated with millions of gay people and their families. The film’s maturity and breadth appealed to mainstream audiences and started a conversation that continues today.

The film’s iconic line – “I wish I knew how to quit you” (actually a bit of dialogue Gyllenhaal tosses off as a grumbling – watch the film again and listen) – prompted countless parodies, many because the poignancy of the line, the yearning, the honest devastation underscored, was just too much for some viewers to bear.

His face scrunched, his jaw locked, every word mumbled, Ledger gives a heartbreaking performance as Ennis, a man at war with himself every day of his life.

As Jack, Gyllenhaal is more open, more optimistic, but Ennis’ refusal to acknowledge the power of what they share and forever keeping him at arm’s length, embitters Jack. Both men starve their whole lives for the love they can only find on that mountain.

No other film had ever dared depict a same-sex relationship over the decades and show with such force how homophobia, both societal and internal, ruins lives.

Ennis and Jack deny their relationship, but the ripples of their lifelong affair devastate Ennis’ wife Alma (Michelle Williams, who is just sublime) and Jack’s wife Lureen (Anne Hathaway in her first serious post-Disney role).

The film swept just every critics circle and awards show and was the front-runner leading up to the 2006 Academy Awards.

In one of the biggest snubs in Oscar history, “Brokeback” lost to “Crash,” the feel-good film about racism.

It’s 10 years later. Which film are we still talking about?

Vice President Joe Biden has said that attitudes toward same-sex marriage changed because of NBC’s “Will & Grace.”

That’s like crediting the Civil Rights movement to “Amos & Andy.“

“Will & Grace” was a minstrel show.

“Brokeback Mountain” challenged mainstream audiences to see that the love between its two men was serious and meaningful. It seems a stretch to credit anything in pop culture with advancing societal change, and yet if anything could plant a seed, it was “Brokeback Mountain.” There had never been such a powerful romance in pop culture – and a decade later, there’s still nothing that matches it.

If you don’t choke up watching this clip of Ennis finally visiting Jack’s home after Jack’s death and discovering the secret he kept even from him, then I have terrible news for you:

You’re dead inside.

“Brokeback Mountain” endures because it captures the truth of the cost of love denied.