After 9/11, you could practically hear the wails coming from regional tourism offices across the country. Fliers’ fears of being on the next hijacked plane ground air travel to a halt, left hotels vacant, and short-circuited the tourism agenda of nearly every city in the country. You’d be hard pressed to find a time when vacationing was so unappealing to everyone.

That is, everyone except gays. While the majority of American travelers remained stationed in their hometowns, gays and lesbians continued to travel in full force, taking advantage of cheap airfare and hotel rooms and spending about $70 billion annually, according to the research firm Community Marketing Inc. It took a terrorist attack for cities to realize that gays have more disposable income and fewer domestic balls-and-chains keeping them at home, and that if you invite them to your city they’ll probably pay you a visit.

“As a group, gays and lesbians experienced very much day-to-day challenge of their own lives, so the thought was, ‘Hey, I’m more afraid of being gay-bashed walking home from a bar late at night then I am of an outside terrorist attack,’” Jeff Guaracino, author of Gay and Lesbian Tourism: The Essential Guide for Marketing, said in a phone conversation.

The discovery of a demographic with $800 billion in buying power (everything left after taxes) that spends significantly more while traveling than its straight counterpart has spurred a new inter-city competition to make cities as gay-friendly as possible. Since the 9/11 attacks, the number of cities in the world with active gay-marketing campaigns has jumped from six to 67. Not all cities have jumped on board, of course. But for the ones that have, it’s meant massive efforts targeting the gay population and a cultivation of cities’ gay districts. In perhaps the most interesting marriage of marketing and progressive policy-making I’ve ever seen, Bloomington, Ind., actually legalized same-sex unions in 2006 as part of an effort to make the city more appealing to gay travelers. While Bloomington hasn’t listed the exact payback from that investment, they did note that the city was a more crowded around the time of their gay and lesbian film festival.

Even now, when the threat is more financial than bodily, gay travelers haven’t pulled back, and some cities are looking towards the gay traveler to help import money into their budgets. While a few cities like my own Philadelphia have axed some of their assistance to gay tourism marketing as part of larger budget cuts, others are taking advantage of the industry’s potentially salutary effects. Last month, for example, Massachusetts launched an LGBT travel website highlighting Boston as an epicenter of tolerance and diversity.

Maybe more cities will take Bloomington’s lead and, in an effort to cash in on their own piece of the gay tourism industry, roll out progressive civil rights policies to invite gays to their cities. That doesn’t mean that cities traditionally less tolerant of gays and lesbians will be able to slap a domestic partnership law on the books and watch as gays come in droves – after all, Bloomington already had the fifth highest number of same-sex partnerships in the country. But it does mean that cities already teetering towards more progressive civil-union rights might be tempted to go through with them, as their own piece of that $70 billion relief dangles in front of their faces.