In voting to remove four public monuments with ties to the Confederacy, the New Orleans City Council has weighed in on a public debate that’s lasted for months, drawing comments from across Louisiana and other parts of the country. What’s been surprising about this controversy is its passion. For the most part, after all, Americans often don’t pay that much attention to monuments after they’re built.

That’s what the late novelist John Updike discovered a few years ago when a magazine assigned him to write an article about America’s most prominent monuments. What Updike learned, in the course of his research, is that for the most part, citizens give these monuments very little thought.

In New Orleans, much of the ongoing debate has focused on what, if anything, to do about the towering statue of Confederate Gen. Robert E. Lee; the council eventually voted to take it down. But consider the memorial erected in honor of Lee’s Union counterpart, U.S. Gen. Ulysses S. Grant. When he died in 1885, Grant, who had risen from military service to the presidency, was arguably the most popular man in America.

“A crowd of over one million attended his funeral and, 12 years later, the dedication, in New York City, of the Grant Monument, popularly known as ‘Grant’s tomb’ — a classical mausoleum comparable in sheer size and costliness only, in 19th Century America, to the Washington Monument and the Statue of Liberty,” Updike told readers. “But over the years the crowds who came to the vast shrine thinned, the last veteran in the Grand Army of the Republic passed away, and Grant’s heroic generalship became diluted, in our shifting historical memory, by our awareness of his weaknesses and the sad corruption of his presidential administration. Warmth has ebbed from Grant’s memorial, though its park is still gratefully used. The eventual fate of all monuments is to become, like the Sphinx, a riddle.”

Updike found other examples of how fickle public opinion about monuments can be. The Washington Monument in the nation’s capital took decades to complete, as enthusiasm waxed and waned about the project. After Pope Pius donated a marble stone for the monument, anti-Catholic feeling further frustrated public support.

The complication of such grand memorials to heroes of the day, of course, is that monuments are meant to be permanent, while public opinion, by its nature, is mutable.

Which means that regardless of what might be erected to replace the monuments of our time, our descendants could very well greet the result with indifference — or even hostility.