One day in the late 1920s or early ’30s, a worker on the Arlington Memorial Bridge project stood before a slab of granite that would become a bench on the structure and drew the notation “P 5” in black paint.

The new arched drawbridge over the Potomac River was to be a symbolic link between North and South, Arlington National Cemetery and the Lincoln Memorial, and, in future years, an avenue for protest, celebration and mourning.

The worker’s notation probably told where the piece fit in the complex assembly.

On Tuesday, 87 years after the bridge opened, slab “P 5” sat on a stack of wooden pallets inside a makeshift work room as William Angel, 40, and Osmar Delao, 50, smoothed its sides with a power tool.

Darkened and chipped, “P 5” was one of hundreds of pieces of stone that were removed from the historic bridge last year for cleaning and repair as part of a $227 million rehabilitation project now underway.

Hunks of curbing, benches and hundreds of ornate 80-pound balusters, for the balustrade, or stone railing, were scattered across a large Lorton Stone company work yard in Upper Marlboro, Md., like pieces of a huge puzzle.

There, they were being power-washed and repaired, if needed, said National Park Service spokesman Jonathan Shafer.

Many of the pieces have been stained by rust over the years from passing cars and nicked by snowplows, said Lindy Gulick, a Park Service architectural conservator.

Missing parts are being replaced by new pieces that are glued in place and sculpted to fit.

The original balusters were handcrafted from stone cut in a quarry in Mount Airy, N.C.

Replacements for the few that could not be repaired are being made with the help of a computer and with stone from the same quarry, Gulick said.

Designed in the neoclassical style in the 1920s by the architectural firm McKim, Mead & White, the bridge is 2,100 feet long.

It has a central draw span that was once the longest, heaviest and fastest-opening in the world. It could be raised in about 1 ½ minutes, according to a 1988 Park Service report.

But the 216-foot drawbridge section has not been opened since Feb. 28, 1961, because other low bridges on the river prevented navigation by taller ships. The antique draw section is being replaced with one that does not open.

The bridge has “never had a full rehabilitation, and it’s time for us to improve its condition so it’s ready for another 80 years of service,” Shafer said.

Work on the south side of the bridge began in 2018 and should be completed this year, Shafer said.

Work will then shift to the north side.

That procedure is being used to permit traffic on the bridge while the repair is underway.

About 68,000 vehicles used the span daily before the project began. Traffic is down to about 51,000 a day, the Park Service said.

Various lane blockages have been in place and will continue. The project is expected to be completed by 2021, the Park Service said.

Memorial Bridge is “more than a bridge,” Shafer said.

Over this nine-arch span walked President Herbert Hoover and first lady Lou Hoover, inspecting the just-finished bridge Jan. 16, 1932, as the country fell deeper into the Great Depression.

The bridge opened to traffic the next day, when more than 30,000 vehicles crossed, according to a news report. The speed limit was 22 mph.

The first funeral procession to Arlington National Cemetery crossed the day after that.

The deceased was Alexander M. Harvey, a Canadian veteran of World War I who had worked on the bridge during its construction.

He had fallen from a building site in Washington five days before and was buried in the cemetery’s section for Canadian war veterans.

His was one of many such send-offs.

Famed World War I Gen. John J. Pershing’s funeral cortege crossed the bridge on a showery day in July 1948.

As a shocked nation watched, President John F. Kennedy’s cortege crossed after his assassination in 1963. The funeral of his brother Robert crossed by moonlight after his assassination in 1968.

The bridge has seen protest marches during the Vietnam War, commemorative walks to mark the Sept. 11, 2001, terrorist attacks, and the armies of motorcycle riders who turned out for Memorial Day’s annual Rolling Thunder rally.

On Tuesday afternoon, Angel and Delao, of Lorton Stone, worked to smooth a new piece that had been inserted into “P 5.” Angel sliced off the rough side with a power tool, while Delao vacuumed away the stone dust.

Nearby rested a small sledgehammer, a bag of chisels and a red pencil.

“For me, in particular, it’s not the first historic job site,” Angel said. He said he had worked on the U.S. Capitol, the Supreme Court and the Washington Monument.

“We’re very proud” to be doing such work, he said.