SINCE HIS death last month, longtime Mayor Thomas M. Menino has been memorialized for any number of qualities: his genuine comfort among constituents; his firm control of City Hall; his enthusiasm for the problem-solving side of the job. He’s also seen as a bridge-builder, one who helped to smooth over some of Boston’s old divisions.

But there is one illuminating episode that has gone all but unmentioned in the various tributes to Menino. In 1997, the city’s first Italian-American mayor officially accepted on behalf of the city a sculpture of Sacco and Vanzetti, the Italian immigrant anarchists executed 70 years earlier after a trial that many have long held was a travesty of American justice.

The sculpture is still on public display now, though barely. As intriguing as it is obscure, it has a complicated pedigree: created by the same man who designed Mount Rushmore, it was repeatedly offered to the city for public installation—and just as often rejected by politicians scared of engaging the raw politics of the Sacco-Vanzetti story.

Menino’s decision to finally accept the sculpture was barely covered in the media. But it went a long way toward resolving one of the most divisive stories in Boston’s long and fractured history. In one small act, Menino gave Bostonians and all Americans—or at least those who know where to find it—a bracing lesson about the deeper meanings of patriotism.

A CENTURY AGO, Americans feared anarchists much as they fear terrorists today. Anarchism, with socialism and communism, had become popular among recent immigrants frustrated by the lack of opportunity they found on American shores, and some of them resorted to violence to gin up publicity for the cause. Followers of the anarchist Luigi Galleani targeted dozens of elected officials across the country, including US Attorney General A. Mitchell Palmer, whose home was bombed in April 1919. Urged on by xenophobic groups like the American Legion, the federal government waged a widespread campaign to suppress radical organizations....