Today, the Museum of Modern Art announced that it acquired the Rainbow Flag as part of its design collection "where it joins similarly universal symbols such as the @ symbol, the Creative Commons logo, and the recycling symbol."
Gilbert Baker created the Rainbow Flag in 1978, and his bio explains, "Baker, born in Kansas 1951, served in the US Army 1970-1972, which stationed him in San Francisco just at the start of the gay liberation movement. His soldier’s story is told in Randy Shilts book “Conduct Unbecoming”. After being honorably discharged Baker stayed in San Francisco and taught himself to sew. It was this skill that he put to use making banners for gay and anti-war street protest marches, often at a moments notice, at the behest of his friend Harvey Milk- later elected to office and assassinated Nov 27, 1978. Milk rode triumphantly under the first Rainbow Flags Baker made at their debut on June 25th 1978, for the San Francisco Gay Freedom Day Parade. Baker credits Milk for inspiring his work with the message of hope."
MoMA's Michelle Millar Fisher interviewed him about the inspiration:
So the American flag was my introduction into that great big world of vexilography. But I didn’t really know that much about it. I was a big drag queen in 1970s San Francisco. I knew how to sew. I was in the right place at the right time to make the thing that we needed. It was necessary to have the Rainbow Flag because up until that we had the pink triangle from the Nazis—it was the symbol that they would use [to denote gay people]. It came from such a horrible place of murder and holocaust and Hitler. We needed something beautiful, something from us. The rainbow is so perfect because it really fits our diversity in terms of race, gender, ages, all of those things. Plus, it’s a natural flag—it’s from the sky! And even though the rainbow has been used in other ways in vexilography, this use has now far eclipsed any other use that it had….
He also had interesting anecdotes about the people who helped him—like "Fairy Argyle Rainbow...She was a hippie girl, was the queen of tie-dye. I knew I wanted to do an organic dye process" and how they actually dyed the material:
I then called another friend of mine, James McNamara—he knew how to sew, he’d been to FIT [the Fashion Institute of Technology in New York] and was the only person who knew how to sew as well as I did. It took four hands to move the fabric through the machine, 20 hands to iron the fabric. I remember one day we had it all in the dye bath—you have to set the dye, and then you have to rinse it out. We looked at each other thinking “we’ll take it to the Laundromat.” Well, they have all these signs at the Laundromat saying “do not dye” so of course we wait until everyone is gone late at night and run into a Laundromat and fill every machine with quarters and blast them all—and [the machines turn] every color of the rainbow! We threw Clorox in [the machines] afterwards hoping that the next customers weren’t walking out of there with pink underwear! It was certainly not like the way they are made today, but I treasure those memories because it really was a beautiful process and I really love all the people who were there.
Here's a glorious image of a flag in NYC, to mark the 25th anniversary of the Stonewall Riots in 1994: