But Mr. Daggett, on trial in 2005, took the witness stand and portrayed himself as a mob target, describing a 1980 episode in which Mr. Barone had put a gun to his head and threatened to kill him and his family — an incident that so terrified Mr. Daggett he urinated in his pants, according to news accounts.

During that trial, one of Mr. Daggett’s co-defendants, a reputed mobster named Lawrence Ricci, went missing. Several weeks after the men were acquitted, Mr. Ricci’s decomposing body was found in the trunk of a car outside a New Jersey diner. The murder, which Mr. Arsenault said is the last known waterfront killing, remains unsolved.

Image Harold J. Daggett, the president of the International Longshoremen’s Association. Credit Thomas Estrin

Mr. Daggett declined, through the longshoremen’s association’s spokesman, to be interviewed. But alluding to his brushes with the Justice Department, Mr. Daggett joked at a union conference in Puerto Rico in 2015 that when he was invited to the White House for a labor meeting, “I thought I might have a better chance ending up in the big house, but there I was, your I.L.A. president, at the White House.”

But Mr. Daggett’s lawyer in that 2005 trial, George Daggett (his cousin), said in a recent interview that “the mob on the waterfront is a myth” — something that has not been true for half a century. Mr. Daggett, who frequently represents longshoremen in litigation with the Waterfront Commission, said that the agency prefers to pretend “we’re still in the ’50s.”

“They can’t say, ‘We got rid of the mob,’ because then there’s no reason for them to be in existence,” George Daggett said. “I challenge them to prove mob influence on the piers. What have they come up with? A couple of guys here and a stray guy there?”

The mob’s grip over the New York waterfront began nearly a century ago and was predicated on a few simple facts: The work was uneven, depending on a ship’s arrival time, and yet the cargo needed to be unloaded quickly, so that produce did not spoil and the shelves of America’s stores could remain stocked. Gangsters quickly realized that the piers were the choke point of the economy, and that a dizzying array of rackets were available to them. They pilfered cargo as it came ashore and extorted truckers who had come to collect cargo or drop it off. And, most cruelly, the mob controlled which of the longshoreman would be selected to work.

Theirs was some of the most dangerous work in the country, but longshoremen had to beg to get it. At the shape-ups on the piers, where longshoremen would gather each morning in the hope of joining the group that would work on an arriving ship, it was common for a man to place a toothpick behind his ear, a signal that he would kick back some of his pay.