Saturday afternoon, Somerville Avenue closed to cars from Church Street to the Union Square municipal lot, and roughly 30,000 people filled in the gap. Fluff jousting on the Shenanigans Stage. A cover band on the Fluff 'N Jam Stage. Free bike valet at two spots along the avenue, because organizers have spent two decades telling people not to bother driving in. Arthur Read, aardvark and Somerville's most durable ambassador via GBH, worked the crowd for photos. The theme this year was "Legally Fluff: A Toast to Union Square," a nod to the fact that a festival born in 2005 just turned old enough to drink.

That's the fun part, and if you were there, you already know it. What's more interesting is the role the festival has played in Union Square, and how the commercial district around it has changed over 21 years.

The festival and Union Square's commercial story

What the Fluff? is a marshmallow-themed street festival in Union Square. Union Square Main Streets, the nonprofit that still runs the event alongside the Somerville Arts Council, organizes it. The festival draws visitors to the square.

As Hoodline reported, the invention itself has its own footnote worth knowing if you live here and have never asked. Archibald Query, a Somerville confectioner, sold his marshmallow spread door to door starting around 1917. In 1920 he sold the recipe for $500 to Durkee-Mower, the company that turned it into the Fluff sold in stores today. Durkee-Mower's factory has run out of Lynn ever since, using a formula that hasn't changed, and the company still manufactures somewhere between 5 and 7 million pounds of it a year, with roughly half of that going to customers in New England and upstate New York.

That's a nice piece of trivia to bring up at a cookout. It's also part of the local history behind the festival and Union Square's connection to Fluff.

The evidence is in what's leasing space right now

Twenty-one years is long enough to look beyond attendance and consider how the commercial district has changed. This year, that story includes several real leases.

Three things are happening in Union Square right now, each occupying a footprint that used to hold something else:

• First Crush, a natural wine bar and event space, is opening this fall at 259 Washington Street, in the space that used to be Juliet Social Club. Juliet Restaurant is still operating in the same block. Owner Gabrielle Malina ran First Crush as a two-year run of pop-up wine events around Boston before landing a permanent home, and she's noted that the new spot sits just around the corner from Counter Culture, where she hosted her very first event.
• Kima Cafe had targeted a mid-September opening at 75 Bow Street, in the former Fortissimo Coffeehouse space, with a menu built around Korean and other Asian influences.
• Workbar signed a July lease for a 10,000-square-foot coworking facility in the square, expanding a footprint that's been part of Union Square's office mix for years.

None of these are new construction. They mark changes in existing commercial spaces: a wine bar is replacing a social club, a café is replacing a coffeehouse, and a coworking operator is scaling up an existing use. Together, they show businesses adapting to the spaces available in Union Square.

As Patch reported, Malina said, "Still in disbelief that we snagged this spot in the heart of Union Square." Her comment conveys excitement about the location.

What this actually tells you about the square

The easy version of this story is "new businesses come to Union Square every year, cool." That's true and also not the point. The point is that Union Square's commercial corridor has changed since the festival began in 2005, and leases offer one way to see that change.

You can see the same pattern in who's showing up to the festival itself. Somerville Mayor Jake Wilson has pointed to local businesses, artists, and volunteers as the reason the event has stayed fresh for more than two decades, and this year's commemorative festival design came from local artist Jen Gubicza rather than an outside agency. The event still runs on the same civic infrastructure it always has. What's changed is the commercial fabric around it.

That's worth knowing if you've lived in or near Union Square for a while and have watched the square go through a few different identities. The square that hosted its first Fluff Festival in 2005 is not quite the same square that now has a wine bar owner planning to open a location here.

What to actually expect this fall

If you're planning your own walk through the square in the next few weeks, here's the practical version. Kima Cafe had been aiming for a mid-September opening at 75 Bow Street, so it may already be pouring coffee by the time you read this. First Crush doesn't have a confirmed date yet beyond "this fall" for 259 Washington Street, so keep an eye on its Instagram if you want to be there on day one. Workbar's 10,000-square-foot buildout is a longer runway and likely won't be visible from the sidewalk for a while.

None of that changes what happened Saturday. The festival closed the streets, 100-plus vendors sold fluff-themed everything, and a costumed aardvark took photos with strangers. That's the version of Union Square that shows up on a poster. The version that shows up in a commercial lease offers a different view of how Union Square's commercial district has changed over the past 21 years.

It looks like it has.

If you're watching Union Square, Davis Square, or any other corner of Somerville and want a read on what a specific block or building is actually worth right now, that's the kind of question Mike Cohen answers for a living. Reach out anytime you want a straight, local take on the market around you.