Washington ? Two cranes sit on a temporary levee at the Tidal Basin. A crew is removing timber piles, replacing them with 41 four-inch concrete caissons and 53 18-inch pipes that are to be sunk 10 feet into the muck. The Jefferson Memorial is a construction site.

The remarkable thing about this scene is that today, when we celebrate the 234th anniversary of American independence, the image of the author of the greatest document in our history is also under construction. Just as his statue and the tranquil temple that surrounds it seemed to have borne a weight too heavy for any mere memorial, Jefferson’s place in history is shifting again.

It does so regularly. Beloved as a librettist of liberty, he was an embattled secretary of state. Frustrated as vice president, he was a controversial president. Embraced by liberals for his expansive devotion to liberty, he later became a hero of conservatives for his conviction that a small, decentralized government was best. Saluted as a troubadour of freedom, he was reviled as a hypocrite for being a slaveholder.

And just this year the Texas Board of Education found itself in a heated dispute over the place Jefferson, who is identified with the separation of church and state, should have in the state’s history curriculum.

This is a lot of weight for one man to bear, and for one monument, which has been sinking into the muddy basin since the memorial was dedicated in 1943, when a war-weary nation had ample reason to join Jefferson in his “hostility against every form of tyranny over the mind of man” — a remark that is carved around the top of the rotunda and that had special meaning in the nation’s second year of warfare against Nazi Germany.

The tourist version of Jefferson never has lost its appeal. Step into his memorial and you will see the magus of Monticello towering above you, looking at a far horizon, gazing at a capital and country he conjured up at the end of the 18th century but very likely would not recognize at the beginning of the 21st century.

His countrymen now come in many colors. They hold cell phones at arm’s length to take his picture; they arrive at one of the most sacred shrines of democracy in shorts and T-shirts. But if the digital age is supposed to shorten our attention spans — some studies suggest it does — here is an island of Enlightenment in an age of Wikipedia.

Here truths are not merely self-evident but enduring. Here we are reminded that the mind was created free. Here we understand that institutions must advance with the times. Here, on the southern wall, is this explanation, from Jefferson himself:

“We might as well require a man to wear still the coat which fit him when a boy.”

Here, too, we — all of us, of any age — wonder how much the coat that fit the Jefferson of our own youth fits him today.

Jefferson, perhaps more than any other figure in our history, certainly more than any other founding father, has changed as the country has changed. One such transformation — a remarkable, completely unanticipated one — occurred when it became evident that he had fathered children with a slave, Sally Hemings.

“If anything it humanized him,” Annette Gordon-Reed, who won a Pulitzer Prize for her account of the Hemings family of Monticello, said in a recent conversation. “He’s no longer a marble statue; he’s a human being with feelings. He’s still very admired, but much more as a person rather than as a mythic being.”

Jefferson was a slaveholder when he wrote that all men were created equal. That fact was known but dismissed for generations. Then, in the 1950s and the 1960s, when scholars and civil-rights activists and eventually the broad population began increasingly to focus on slavery, Jefferson became less a figure in the pantheon of American heroes than a problem in American history.

George Washington and James Madison also were slaveholders — a dozen American presidents were — but only Jefferson wrote the Declaration of Independence.

And so Jefferson took the brunt of the criticism, even though about half the founders were slaveholders. But the irony of Jefferson’s fragile position among the exalted is that his standing has been eroded in large measure by a biography of one of his nemeses, the John Adams volume written by David McCullough that sold more than a million copies and spawned a mini series.

“People seem to have a need to be a Jefferson admirer or an Adams admirer,” says Joyce O. Appleby, an emeritus professor of history at UCLA and the author of a recent Jefferson biography. “We have a tremendous investment in the personalities of our founding fathers, so the ascent of crusty old John Adams was at the cost of Thomas Jefferson.”

Yes — but.

Jefferson and Adams were antagonists at the end of the 18th century and at the beginning of the 19th. And the two men were inextricably connected.

Jefferson’s secret dissent from the Alien and Sedition Acts — he wrote the Kentucky Resolutions that assailed these measures — helped to doom Adams’ re-election prospects. Jefferson’s victory in 1800 is often described as the Revolution of 1800.

But once their presidencies were behind them, the two embarked on a remarkable correspondence — remarkable as much for its content as for the warmth of the exchange that occupied them for the last 14 years of their lives.

They died the same day — July 4, 1826, exactly 184 years ago. It was the 50th anniversary of the Declaration of Independence, and an eerie occurrence — can it be merely a coincidence? — that makes us tremble when we reflect, as the deist Jefferson put it, that God is just.

— David Shribman is executive editor of the Pittsburgh Post-Gazette.