From the San Diego Museum of Man to Boston's City Hall, more than 50 buildings and structures across the country lit up in orange Wednesday night to mark one month since the Las Vegas massacre, in honor of the victims of the biggest mass shooting in modern U.S. history.

Scott Rechler, chairman and CEO of New York-based RXR Realty, worked with the gun-control organization to launch the campaign.

"It's a hope to try to get people to light and unite and have a voice about trying to force leadership to address this crisis," Rechler told NPR in an interview.

Orange has become a symbolic color against gun violence following the 2013 shooting death of Hadiya Pendleton in a Chicago park. The 15-year-old was killed a week after performing at President Obama's inaugural parade. Hadiya's friends say they chose orange to remember her because it is the color hunters wear to show they should not be targeted.

Rechler said some structures declined to join Wednesday's campaign because they did not want to make a political statement. Those that did participate include Wisconsin's Madison Public Library, Children's Hospital of Philadelphia, Skydance Bridge in Oklahoma City and the Helmsley Building in New York City.

The Helmsley Building, which is owned by RXR Realty, will remain aglow in orange for 58 nights to represent each victim of the Oct.1 shooting at the Route 91 Harvest music festival on the Vegas Strip.

Rechler said the building has been lit up from time to time, including after last year's mass shooting at the Pulse nightclub in Orlando, Fla. "There's a general belief ... that business leaders need to take up and have a greater voice on social issues, as we've seen less and less action by our elected officials in Washington," Rechler said.

The New York Times reports that as people grapple with mass tragedies, lights on landmarks are frequently used as communal displays of mourning.

Following the Paris attacks of 2015 that left 130 people dead, red, white and blue — the colors of the French flag — illuminated the world's most iconic structures, from the Pyramids of Giza, to the Sydney Opera House, all the way to the Christ the Redeemer statue in Rio de Janeiro.

New York's Empire State Building often uses its tower lights to honor victims of attacks or tragedies. And the Eiffel Tower took the opposite approach of cutting its lights and going dark last month after the deadliest bomb attack ever in Somalia.

"I think buildings have that symbolism of ... speaking for the community and creating awareness," Rechler said. "Sometimes it's the symbolic moments that actually are the ones that create the change."

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