Separation of church and state is one thing, separation of religion and history quite another — except for the group American Atheists.

So offended is American Atheists Inc. by the Ground Zero Cross, it sued the Port Authority for leasing land to the National Sept. 11 Memorial & Museum — a private nonprofit that the group is also suing for planning to exhibit the cross in a display that shows how rescue workers dealt with the traumatic post-9/11 recovery efforts.

On Thursday, the Second Circuit Court of Appeals will hear American Atheists Inc.’s argument that the display violates the First Amendment’s Establishment Clause.

The Ground Zero Cross is just one of many pieces in the yet-to-open display, but one that captured the attention of many Americans from the start, signaling hope amidst the carnage.

Excavator Frank Silecchia was the first to notice the 17-foot steel crossbeam shaped like a Latin cross jutting upward from the wreckage. At his request, the Rev. Brian Jordan, a Franciscan priest performing rites at Ground Zero, blessed the cross as a point of refuge.

Work crews, family, friends of lost loved ones and grieving New Yorkers frequently visited the cross for consolation, rest and — yes — even to worship. Sometimes hundreds would gather for services regularly held around the cross.

And it wasn’t just Christians. Many of other faiths or no faith at all — despite finding no religious significance in the steel crossbeam — recognized and shared the hope and strength it inspired.

And many added their own inspiration. As noted in the museum’s brief in the American Athiests case, ironworkers cut miniature Stars of David, Maltese crosses and outlines of the Twin Towers and the Manhattan skyline as religious and secular “tokens of comfort” for rescue workers and victims’ families. Many of these will also be included in the museum’s historical display.

And rightly so. We all ought to remember the solidarity of hope that arose from the tragedy at Ground Zero.

In fact, even American Atheists Inc. has been compelled to acknowledge that the Ground Zero Cross is more than just a religious symbol — it is part of our history, part of an incredible story of overcoming the most harrowing circumstances. In its appeal brief, the group notes that it has dropped its bid to ban the cross, admitting that “rewrit[ing] history” is not “the most desirable remedy.”

Its fallback proposal is for the display to include some atheist symbol — perhaps a giant “A” for “Atheist.”

This course correction only underscores the lawsuit’s ridiculousness. The display also includes an urn of holy water from the nine rivers of India gifted to Mayor Rudy Giuliani and a silver plate featuring images of the Buddhas of Bamiyan from the people of Afghanistan.

Should courts entertain lawsuits by non-Hindus and non-Buddhists challenging these artifacts as an offense or urging the display of a giant “E” for “Everyone Else”?

The absurdity is obvious. We are not injured, but enriched, by remembering history as it actually happened, religion and all. The Second Circuit would be wise not only to find no violation of the Establishment Clause in this case, but no right to sue in the first place.

Eric Baxter is senior counsel for The Becket Fund for Religious Liberty, a nonprofit law firm dedicated to the free expression of all faiths. He filed a friend-of-the-court brief before the Second Circuit in this case.