In Washington, members of both parties lauded the senator as a man who embodied the American dream.
"Michelle and I were deeply saddened to learn of the passing of Sen. Frank Lautenberg, a proud New Jerseyan who lived America's promise as a citizen and fought to keep that promise alive as a senator," President Obama said.
Vice President Biden and Secretary of State John Kerry, both longtime Senate colleagues, praised him.
On the Senate floor, Lautenberg's desk was covered in a black cloth topped with white roses. Flags at the Capitol were at half staff.
"Few people have contributed as much to our nation and to the U.S. Senate as Frank Lautenberg," said Majority Leader Harry Reid (D., Nev.).
Sen. Lautenberg, proud and combative, fought for public safety initiatives - waging battles to ban smoking on planes, set a national minimum drinking age, strengthen environmental protection, and tighten gun laws - while relishing sharp-edged politics throughout his career.
He had decided not to seek reelection in 2014.
"This is a man who always put his country first," Biden said in a recording posted online. "He could have won [reelection], but I think he knew, he knew, that his health would not permit it. I'm going to miss him a lot."
Sen. Lautenberg loved the prestige of the Senate and jousting with powerful political opponents, focusing lately on the gun lobby. On April 17, as the Senate considered a series of bills to strengthen gun laws, an ailing Sen. Lautenberg was wheeled onto the chamber's floor to raise his hand and vote "aye."
That day, Sen. Richard Blumenthal (D., Conn.) called him "a great champion and a warrior." It was one of Sen. Lautenberg's last votes.
The son of Russian and Polish immigrants whose father died when he was 18, Frank Raleigh Lautenberg wanted others to have the same opportunities that helped him rise, friends said.
"He lived the American dream, and he valued that," said Brad Lawrence, a political consultant who worked on Sen. Lautenberg's 2002 campaign, and he wanted to ensure that others could follow a similar path to success.
"He came from very humble background, he became very wealthy, but he really never forgot his roots," said U.S. Rep. Frank Pallone (D., N.J.), who volunteered on Sen. Lautenberg's first campaign, in 1982, and worked closely with the senator in Washington.
Senate Minority Leader Mitch McConnell (R., Ky.) called Sen. Lautenberg "a patriot whose success in business and politics made him a great American success story."
Sen. Lautenberg sponsored landmark bills raising the national drinking age to 21 and lowering the threshold for drunken driving.
He was an advocate for the families of those killed in the bombing of Pan Am Flight 103 over Lockerbie, Scotland, and pushed for heightened airport security.
His 1987 law barring smoking on short domestic flights opened the door for the no-smoking laws that have become common in public spaces across the country.
Sen. Lautenberg was an outspoken critic of the second Iraq war, opposed restrictions on abortion, and favored expanded rights for same-sex couples.
Friends said Sen. Lautenberg's drive for tighter environmental laws and worker protections were fueled by the death of his father, Samuel, from colon cancer after working many years in silk mills.
After that, he told the New York Times in 2002, "our whole life became so enveloped with sadness."
Always he worked to bring transportation funding back to his traffic-congested state. A major rail hub in Secaucus bears his name.
Sen. Lautenberg loved the Senate limelight and skiing at ritzy Colorado destinations, but friends also recalled a working-class side that adored New Jersey. Former aide Karin Elkis remembered a campaign ad in which Sen. Lautenberg bit into a New Jersey tomato. After events at the Shore, Pallone said, the senator would insist on a side trip to Max's Famous Hot Dogs in Long Branch.
Despite his long tenure, Sen. Lautenberg never acquired the power or broad influence that comes with a committee chairmanship, in large part because he lost his seniority after his initial retirement in 2000. Instead, Sen. Lautenberg was known as a nuts-and-bolts lawmaker, more workmanlike than visionary.
As he neared the end of his fifth Senate term, health problems diminished his role in Washington. He overcame stomach cancer in 2010 but recently was absent for long stints. A bout of flu and bronchitis late last year forced him to miss votes on a relief package to help New Jersey recover from Sandy. Then, leg pain and weakness limited him. He rarely had been in Washington since the end of February.
In one stretch, he was out for more than a month as the Senate took up the debate on guns, an issue he had long championed, though he returned for the vote.
"He always struck me as someone very proud of his success, both in business and in politics," said David Eichenbaum, a media consultant who ran Sen. Lautenberg's 1994 campaign. "He was a personality that was fierce and fiercely proud."
Sen. Lautenberg's campaigns took on that personality, Eichenbaum said. "He never wanted any attack to go unchallenged."
One early opponent called him a "swamp dog," a label that stuck throughout his career.
During that same 1988 campaign, Sen. Lautenberg famously said, "A lot of people like their politics the way they like their hockey: rough."
He once called Vice President Dick Cheney a "chicken hawk" as he defended Kerry, then the Democratic presidential candidate, against attacks on his military career.
Even Democrats weren't safe.
Sen. Lautenberg had notoriously frosty relationships with fellow New Jersey senators, including an open feud with Democrat Robert Torricelli, and waged ferocious political campaigns.
As ambitious New Jersey Democrats maneuvered to replace him last year, Sen. Lautenberg suggested that the most forward of them, Newark Mayor Cory Booker, deserved the kind of "spanking" he would give his children for disrespect.
Senator was the only elected office Sen. Lautenberg ever held. He served from 1983 through 2000, retired, and almost immediately regretted the decision. He missed the job and got a chance to return in 2002, added to the ballot as a replacement after Torricelli's campaign imploded in scandal.
Unlike many elected officials, Sen. Lautenberg didn't come up through the party ranks. Wealth paved his path to politics, but only after growing up with little.
Born Jan. 23, 1924, in the working-class city of Paterson, he grew up on such a tight family budget that his parents argued over a bicycle his mother bought for his 13th birthday, Sen. Lautenberg said in a 2005 interview with Rutgers University historians. Tears rolled down his face, he recalled 68 years later, as his father persuaded her to return it.
"We couldn't obligate ourselves like that, a dollar a week. So that stuck in my mind," he said.
He lived in about 13 towns as a child, he said in the Rutgers interview. Sen. Lautenberg's father worked a variety of jobs, including selling coal and taking work in silk mills.
Sen. Lautenberg, who graduated from Nutley High School, worked for a time in a luncheonette run by his mother, Mollie, and enlisted in the Army, serving in Europe in the Signal Corps.
After the Army, he attended Columbia University on the GI Bill.
"That was a life-changing experience," he said in the Rutgers interview. He added, "It wasn't the subjects; it was the horizon that it gave me, and that's what has to be remembered. If you give nutrition to a plant, it grows. If you give nutrition to a child, it grows. When you take a mind that can learn and you give it nutrition, by giving it an opportunity to learn, it grows."
"I went from the back of a store to sitting at the desk that was occupied by Harry Truman before me. I still have the same desk," he said.
Sen. Lautenberg graduated from Columbia's business school in 1949. Dwight D. Eisenhower, then the college's president, handed him his diploma.
A few years later, after selling insurance, Sen. Lautenberg joined two friends who had begun a company processing payrolls.
He helped build the fledgling company - Automatic Data Processing (ADP) - into a giant. The company went public in 1961 and now employs 57,000 people worldwide. It also made Sen. Lautenberg rich: his net worth as of 2010 was valued at more than $40 million, according to the 2010 Almanac of American Politics.
Sen. Lautenberg rarely missed a chance to mention his military service and ADP. He was generous with his fortune, giving heavily to a cancer center in Israel that bears his name and to Columbia, among other causes, and once chaired the philanthropic United Jewish Appeal.
He had a hand in politics long enough to have been on President Richard M. Nixon's "enemies list"; he had donated $90,000 to George S. McGovern, the Democratic presidential candidate in 1972.
But he didn't jump into the fray himself until 1982, when, at 58, he decided to run for an open Senate seat. He was serving his fourth year on the commission of the Port Authority of New York and New Jersey.
Sen. Lautenberg poured more than $5 million into the race, narrowly defeating two-term Republican U.S. Rep. Millicent Fenwick, a colorful and independent member of the House. Although Sen. Lautenberg chafed at the accusation that he made a campaign issue of Fenwick's age - she was 72 - political historians say he painted her as an eccentric out of touch with New Jerseyans and questioned her "fitness" to do the job.
"It was really a tough kind of thing, that I have to run against such an elegant person, and do what I did, which was to suggest that coming in as a freshman senator, she, at age 72, would have a long way to go before she could be effective," he told Rutgers in 2005.
In 1988, seeking his second term, Sen. Lautenberg faced a challenge from Pete Dawkins, a Vietnam veteran, retired general, multimillionaire, and one-time Heisman Trophy winner. The Chicago Tribune called the race "a mudslide."
Sen. Lautenberg had help from Democratic consultants Paul Begala and James Carville, who would go on to national renown four years later when they would guide Bill Clinton's successful campaign for the presidency.
It was Dawkins who dubbed Sen. Lautenberg a "swamp dog." Allies had a different name. They called him a "liberal lion."
In 2000, Sen. Lautenberg decided to leave the Senate. Friends and relatives had urged him to go out on top, Elkis, the former aide, said.
"He was never happy after he left the Senate. It was the worst decision he ever made," she said. "He missed the ability to help people. He was always a doer."
Sen. Lautenberg also missed the status and excitement of life as a senator, but he would soon have a chance to return, thanks to missteps by his old rival Torricelli, who was dumped by New Jersey Democrats in 2002 as his poll numbers tumbled amid ethics charges.
Well-known and able to self-finance a campaign, Sen. Lautenberg, 78, spent $1.5 million to beat Republican Doug Forrester.
He was elected shortly after the Senate had voted to authorize the use of force in Iraq. Sen. Lautenberg strongly opposed the war and displayed photos of troops killed there in a foyer outside his Senate office.
He also took immense pride in his long tenure.
"There's a courthouse here that carries my name. There's a railroad station that carries my name, and I'm proud of the service I gave," he told Rutgers.
Longtime Senate colleagues poured forth with tributes Monday. "I will always be grateful and touched by the ferocity with which Frank defended me many years ago," said Kerry. He called Sen. Lautenberg "an American original, and as decent a person as I've ever known in public life."
On the day he announced that his current term would be his last, Sen. Lautenberg left the Senate floor by a side door and said he felt "disconsolate."
"I liked serving here," he said.
Sen. Lautenberg is survived by his wife, Bonnie Englebardt Lautenberg; children from his marriage to Lois Levenson (which ended in divorce) Joshua, Ellen, Nan Morgart, and Lisa Birer; stepdaughters Danielle Englebardt and Lara Englebardt Metz; and 13 grandchildren.
A funeral is scheduled for 11:30 a.m. Wednesday, June 5, at Park Avenue Synagogue, 50 E. 87th St., New York City, following which the body is to be taken to the Secaucus train station that bears his name, and later to Washington. Burial will be at Arlington National Cemetery.
Contact Jonathan Tamari at firstname.lastname@example.org or follow on Twitter @JonathanTamari. Read his blog 'Capitol Inq' at www.philly.com/CapitolInq.
Joelle Farrell contributed to this article.