Corporate signs are proliferating on Boston office towers. Here’s why.

HarbourVest joins a growing list of corporate names that now grace Boston’s skyline: Foundation Medicine, CarGurus, Eli Lilly, State Street, Whoop, MassMutual. Next up: John Hancock. The life insurer took its signature logo that once loomed over the center field scoreboard at Fenway Park and just this past weekend put it up at 200 Berkeley St., below its famous weather beacon.

This surge in office signs started in the early 2010s when Vertex Pharmaceuticals opened its new headquarters on Fan Pier. Then came signs touting the likes of Goodwin, PwC, Reebok, and Converse.

But before Vertex, getting a tower sign through City Hall was next to impossible. Former mayor Thomas M. Menino was notoriously averse during his two decades in office, which ended in January 2014. The exceptions that proved the rule: State Street — one of Boston’s biggest companies — managed to get its name atop One Lincoln (the sign that HarbourVest just replaced) and John Hancock did the same at its since-vacated headquarters on Congress Street in the Seaport. Other than that, the doors were essentially shut.

Not anymore. Count real estate lawyer Dan Dain, author of “A History of Boston,” as a fan of the shift, especially among the Seaport’s similar-looking structures.

“It anchors buildings in place. Particularly in a neighborhood that has some significant design challenges, I think there’s value to it,” Dain said. “And we should be proud of the companies here. It’s a major selling point of Boston.”

But Alison Frazee, head of the Boston Preservation Alliance, said city officials should at least have some clear standards in place. She said she’s concerned about the skyline getting “cluttered with corporate ads.”

If Menino were still alive, he would probably agree.

He didn’t like the idea of putting corporate names on T stations. Legal Sea Foods couldn’t get a sign for its fish processing center on the waterfront, and commissioned a metal cod sculpture instead. Even hotels weren’t a slam dunk. Greater Boston Chamber president Jim Rooney said the Menino administration was initially reluctant to approve a sign on the Westin hotel alongside the Boston Convention & Exhibition Center, at a time when Rooney oversaw the convention center. And Rooney had been Menino’s chief of staff.

“The aesthetics of the city were crucially important to him,” said Dot Joyce, Menino’s longtime press secretary. “That stemmed from the ‘70s and ‘80s and seeing the city become a little run down and looking old and shabby, and wanting to project an image that the city was forward-looking and clean and welcoming.”

But Menino apparently warmed up to some signs over time. As LED screens replaced neon, Joyce said, the Menino administration approved a few digital signs, including an upgraded version of the Citgo sign in Kenmore Square.

“Everything was on a case-by-case basis, to make sure it fit and maintained the fabric of our city’s culture,” she said. “Just because something looks good on a letterhead doesn’t mean it belongs on the top of a building.”

This approach apparently benefited Vertex, which Menino helped lure to the Boston waterfront from Cambridge. Prominent Vertex logos went up, prompting “sign envy” among some executives plotting moves of their own.

Martin J. Walsh, mayor from 2014 through 2021, took a more generous attitude than his predecessor, as recalled by Brian Golden, who led Walsh’s Boston Planning & Development Agency.

Informally, the Menino administration set a high bar: To get a tower sign, a company needed to make the building its headquarters and be its sole office tenant. Walsh loosened that to 75 percent, and then later 50 percent. “Regional” headquarters could count too, Golden said. The hope was to stoke economic development by encouraging companies to call Boston home, while avoiding a mass proliferation of signs.

“Everyone felt strongly that you can’t commercialize the skyline,” Golden said. “You do go to cities and see it on every building. But we thought you can open the aperture a bit without letting it get out of control.”

Under Golden’s leadership, the BPDA tried in 2015 to create formal sign regulations, written parameters that would make it clear what was allowed. But by the spring of 2017, Golden and his team essentially gave up. It simply proved too complicated, he said, given the individual nature of each request.

Mayor Michelle Wu’s administration recently approved a sign for Foundation Medicine’s new home in the Seaport, as well as the John Hancock sign in the Back Bay. Wu said city officials pay close attention to aesthetics and corporate commitments to the community when approving the requests.

“The look of our skyline is really important,” she said. “In these cases where we have worked to showcase the company names, it really reflects conversations about the design, the placement of the logo itself, as well as their commitment and connection [to] Boston and our neighborhoods.”

In John Hancock’s case, the approval remains in effect for as long as the life insurer’s US headquarters remains there.

“You’re starting to think about Vegas [with] all these signs,” said Michael Rubin, real estate co-chairperson at law firm ArentFox Schiff’s Boston office. “I do think it’s an example of the city’s growth and that it’s being recognized for what it really is: a large national and international city.”

The promise of a prominent tower sign can help seal a deal for a marquee tenant. For example, head of global realty Dustin Sarnoski said it was important for State Street’s name to be atop its new headquarters, at One Congress St., to show that the company is a significant part of Boston’s history and its future.

It wasn’t that long ago when the best that most tenants could hope for was a plaque at a lobby entrance. A tower sign, in comparison, builds almost instant brand recognition, said Wil Catlin, at Boston Realty Advisors. Catlin cites the recently installed CarGurus logo atop a tower at 1001 Boylston St., where the online auto marketplace will relocate next year from Cambridge.

“Now, it’s just the CarGurus building,” Catlin said of the tower over the Massachusetts Turnpike. “Everyone who drives underneath it knows it. And they haven’t even moved in yet.”

That wasn’t the main reason CarGurus chose it, real estate director Robert Mirabello said. “[But] the idea we could have our name interwoven into the fabric of the skyline was a nice cherry on top,” he said.

Then there’s One Lincoln. Will it be known as the “HarbourVest Tower,” after nearly two decades with State Street’s name?

Developer John Hynes said he walked by a few weeks ago, and it got him thinking about the change in attitude in City Hall. He was involved in the original permitting for One Lincoln. Now, Hynes has signage rights of his own to offer, to a tenant that occupies at least half of a building he’s developing at 10 World Trade Center Ave. in the Seaport.

“All these buildings with vacancies, they’re all going to have signs on them in the next three years,” Hynes said. “I don’t know if that’s a good or a bad thing . . . but it’s definitely a thing.”

Jon Chesto can be reached at jon.chesto@globe.com. Follow him @jonchesto.