Apple CEO Tim Cook speaks during an event to announce new products in San Jose, Calif., Tuesday, Oct. 23, 2012. (AP Photo/Marcio Jose Sanchez)

Maybe someday we'll complain about Corporate America's shortage of LGBT executives, just as we complain now about the number of women and minorities at the top. And that will be an improvement -- because once Corporate America barely acknowledged that LGBT executives existed.

That changed abruptly on Thursday, when Apple CEO Tim Cook announced, in an essay for Bloomberg Businessweek, that he was gay. That made him the first openly gay CEO of a Fortune 500 company.

It's a watershed moment not only in the history of Corporate America, but in the history of the country.

A couple of other members of the C-suite have come out in the past, including former Urban Outfitters CEO Glen Senk and John Browne, the former BP CEO, who came out after he resigned. But Tim Cook is different.

Because Tim Cook doesn't just run any company. He runs Apple, for God's sake, the biggest company by market value in America, bigger than Exxon Mobil and Microsoft. Apple, the iconic American success story that started in Steve Jobs' garage and became the world's gold standard for fancy consumer gadgets.

The thought that the captain of such an enterprise would be openly gay would have been unthinkable, say, 18 years ago, when President Clinton signed the gay-baiting Defense Of Marriage Act into law.

Today it is not only thinkable, but blissfully mundane: On Wall Street, the news caused barely a ripple in Apple's stock price, which was down about 0.6 percent in recent trading.

Wall Street has come a long, long way from its days of rampant homophobia, but you can bet that if stock traders thought Tim Cook being gay was somehow bad for Apple's business, then the stock would be down a bunch. It's not. This kind of reaction says something about how far the country has come in its attitudes about people's sexual identities. It could encourage other LGBT executives to come out, too.

Of course, Cook's coming-out wasn't exactly a huge shocker: As he wrote, many people inside Apple knew he was gay. Many people outside of Apple were aware of it, too: The business and tech media have long chattered about when Cook was going to finally just make it official, already.

But the fact that Cook could rise to the very top of the biggest company in America, without hiding who he really was, is also an encouraging sign.

Maybe it will give hope to the many LGBT Americans who still face discrimination at work. More than half of all LGBT workers hide their orientation at work, according to a recent Human Rights Campaign survey, as reported just a couple of days ago by CNN. It's still legal in 29 states for employers to fire workers for being gay, CNN noted.

Cook mentioned that, too, suggesting it was part of the reason he broke his silence:

"I’ve had the good fortune to work at a company that loves creativity and innovation and knows it can only flourish when you embrace people’s differences," Cook wrote. "Not everyone is so lucky."

The tide of public opinion and laws in this country has already turned in favor of gay marriage. Maybe Cook's coming-out can help turn the tide more decisively against workplace discrimination, too. As Cook noted, it's bad for business.

Cook has been CEO of Apple for more than three years. Apple's stock price has nearly doubled in that time, and America's lust for Apple products doesn't seem to have cooled a bit. Still, Cook hasn't quite been able to escape the huge shadow of his iconic predecessor. People have wondered if the company can ever be as innovative and efficient under Cook as it was under Jobs. Would the Apple Maps debacle have happened on Steve Jobs' watch? What about bendgate?