“This has been the proudest accomplishment of my life,” said John Rosenthal, a real estate developer who attached the billboard in 1995 to the side of a Lansdowne Street parking garage he owned.

It is the kind of stark message that has made the 252-foot-long billboard a graphic, look-at-me advertisement for stricter gun control. But after 19 years, its owner is searching for a new home.

The mega-billboard facing the Massachusetts Turnpike between Fenway Park and the Citgo sign has long been a landmark of grim tidings. On Monday, its updated digital counter read, “45,864 Americans killed since the massacre at Sandy Hook.”


The sign — the work of Stop Handgun Violence, a Newton nonprofit cofounded by Rosenthal — must be moved by March, a deadline set by the parent company of the Boston Red Sox when it bought the

garage from Rosenthal in 2013.

“I’m hopeful that we’ll find a property owner who shares our concern about gun violence,” Rosenthal said. “We cannot afford to pay a high rent, and the billboard will just cease to exist if that’s the only option.”

Rosenthal said he is searching for sites along the Turnpike, Interstate 93, Route 128, “or anywhere in Boston.” Mayor Martin J. Walsh said he will support a new home in the city for the billboard, which he called “an eye-opening reminder of the tragedy of the crimes being perpetrated with guns across our nation.”

Over nearly two decades, the billboard and its sponsor have attracted support from a broad coalition of gun-control activists, ranging from politicians to artists to families affected by gun violence.

“I was hoping to be able to keep it where it is,” Rosenthal said.

A spokeswoman for the Red Sox declined to comment on whether Fenway Sports Group, the team’s parent company, would be willing to discuss an extension for the sign on Lansdowne Street. She also declined to discuss the company’s plans for the site.


Rosenthal is not required to pay rent for the billboard, but he estimated that the site could fetch more than $1 million a year for commercial advertising.

The developer said that Fenway Center, a mixed-use project he plans to build nearby over the turnpike, might be an option for the billboard. However, he said, the sign cannot be moved there for at least three to four years because of construction, and its location atop the turnpike would not be as highly visible.

Visibility is not an issue now. The billboard, which is passed by 150,000 vehicles a day, is intended to change minds with jolting, in-your-face messaging. The latest example is its tally of US gun deaths since the fatal shooting of 20 first-graders and six adults at the Sandy Hook Elementary School in Newtown, Conn., in December 2012.

Along the bottom of the billboard are 20 colored handprints representing the children gunned down at Sandy Hook. An accompanying message in large, upper-case letters reads: “Assault weapons have stopping power. Fortunately, so does your vote.”

The display usually changes once a year with messages such as, “Welcome to Massachusetts. You’re more likely to live here.” Another design used piecemeal script usually associated with ransom notes: “We have your president & Congress,” in which it likens the National Rifle Association to a hostage-taker.

For baseball fans walking to Fenway Park, the message is unavoidable.


“There is not a time when, if I’m on the Pike or walking to the ballpark, I will not look at that billboard,” said House Speaker Robert DeLeo, a Winthrop Democrat who is close to unveiling a comprehensive set of gun-control legislation. “It’s very simple, but I can’t think of another more powerful [sign] that I’ve ever seen.”

What some people call powerful, others call incendiary.

“It’s a waste of time and money on a billboard that hasn’t solved any problems,” said Jim Wallace, executive director of the Gun Owners’ Action League, which is the Massachusetts affiliate of the National Rifle Association.

“When he talks about the NRA buying Congress or banning assault weapons at gun shows because terrorists are buying them, I think they’re meant to be inflammatory and . . . don’t exactly seek to solve problems,” Wallace said.

Gun advocates, Wallace among them, say tougher regulations do not result in fewer gun deaths.

According to state data, the total number of firearm injuries — including assaults, accidents, deaths, and suicides recorded at a hospital — declined 42 percent from 1994 to 2011, according to the state Department of Public Health.

After a stark drop from 1994 to 1998, however, the number has risen 17 percent.

Rosenthal attributes the increase after 1998, in part, to cuts in federal funding for law enforcement under former president George W. Bush, who served from 2001 to 2009. Despite that rise in gun-related injuries, the state has the second-lowest rate of firearm deaths in the country, according to the federal Centers for Disease Control and Prevention.


“We have become the NRA’s worst nightmare,” Rosenthal said. “Gun laws work, and look no further than urban, industrial Massachusetts if you want to reduce gun violence nationally.”

The focus of Stop Handgun Violence has been reducing gun violence without outlawing firearms, said Rosenthal, who is a gun owner. Instead, Rosenthal said, the group explores “how are kids, criminals, and the mentally ill accessing guns, and what can be done without banning guns?”

Don Law, the concert promoter and an early major donor to Stop Handgun Violence, said the billboard has played a big role in shaping the debate in Massachusetts, where a 1998 law toughened licensing requirements.

“When John set down this path, I said, ‘I’m in,’ ” Law recalled. “We were losing so many young people to firearms. When you sit and listen to how it tears apart individual family members and the whole community, it’s just appalling that we can’t do anything about it.”

The billboard, he said, uses photos and escalating numbers to remind those passing “that these are people, and that these are the kinds of tragedies that are happening in neighborhoods across the country.”

The singer Bonnie Raitt, a longtime supporter of Rosenthal’s, said his effort has been effective. “The Massachusetts handgun campaign is the most inspiring and effective in the whole country,” Raitt said.

Brian MacQuarrie can be reached at macquarrie@globe.com.