(CNN) -- U.S. officials formally declared an end to the worst oil spill in U.S. history Sunday, a milestone that followed nearly five months of dashed hopes and blistering criticism of nearly everyone involved.

After a weekend of pouring cement into the base of the ruptured well in the Gulf of Mexico, pressure tests conducted early Sunday confirmed the seal was holding, former Coast Guard Adm. Thad Allen said announced. The Interior Department agency that regulates offshore drilling pronounced the well dead at 5:54 a.m. (6:54 a.m. ET), Allen said in a written statement.

"With this development, which has been confirmed by the Department of the Interior's Bureau of Ocean Energy Management, we can finally announce that the Macondo 252 well is effectively dead," said Allen, the federal government's point man on the disaster.

The spill saw oil-patch jargon like "junk shot," "static kill" and "blowout preventer" join the American lexicon, triggered shakeups in government and industry and left Gulf Coast residents frustrated and worried for their livelihoods.

"We made our living this year. I don't know about next year," said Scott St. Pierre, a shrimp boat captain from Galliano, Louisiana.

The well, owned by petroleum giant BP, spewed an estimated 4.9 million barrels (206 million gallons) of crude into the Gulf of Mexico before it was temporarily capped July 15. It was permanently sealed only when BP drilled a separate relief well into the sea floor, intercepting the original well and allowing workers to fill it with cement from below.

The disaster began with an April 20 explosion aboard the oil rig Deepwater Horizon, about 40 miles off the coast of Louisiana. The blast claimed the lives of 11 workers aboard the platform, which sank two days later in nearly a mile of water.

The rig's blowout preventer, a massive fail-safe device at the seabed, failed to operate after the blast. Efforts to activate it using remote submarines failed. An effort to plug it with heavy drilling fluid and cement failed. A bid to jam it shut by pumping it full of debris also failed.

Over the spring and summer, as oil washed up on beaches in Louisiana, Mississippi, Alabama and Florida, tourists stayed away from the region's white sands in droves. At one point, federal and state authorities had shut down more than a third of the Gulf to fishing, and a temporary federal ban on deepwater drilling idled oil workers.

St. Pierre said he has spent most of the last four months working for BP, which hired his boat and crew to drag absorbent boom around oily waters, and has not yet returned to fishing. In the meantime, he said, fishermen have lost market share to imports, buyers are still leery of eating fish from the region and no one knows what impact the spill will have on next year's catch.

"The prices are not good. Consumer confidence is low. You can't sell the shrimp," he said.

And Barry Deshamp, a charter boat skipper in Long Beach, Mississippi, said his bookings were down 70 percent over the summer. Many of the people who did go out "were scared to eat the fish," he said.

"All of them were real scared of the oil," Deshamp said. "A lot of them didn't want to keep the fish. Everybody was playing it safe."

BP said Sunday it has paid hundreds of millions of dollars in claims for damages to people like St. Pierre and Deshamps and billions to try to seal the well. In a company statement Sunday, outgoing BP chief executive Tony Hayward called the cementing "the final step in a complex and unprecedented subsea operation."

"However, there is still more to be done. BP's commitment to complete our work and restore the damage done to the Gulf of Mexico, the Gulf coast and the livelihoods of the people across the region remains unchanged," Hayward said in a company statement Sunday afternoon.

BP said the spill had cost it $9.5 billion as of Saturday. The company agreed in June to set aside $20 billion for to pay the costs of the disaster, for which it is liable under federal law.

Hayward became a lightning rod for critics of the company in the wake of the disaster -- particularly after his attempt at an apology in May, when he told reporters in Louisiana that "There's no one who wants this over more than I do. I would like my life back." In July, BP announced Hayward would be replaced by Bob Dudley, the company's managing director, who grew up in Mississippi.

Dudley said last week that the spill eventually would cost the company $32 billion.

At the White House, President Barack Obama hailed the "final termination" of the well Sunday but said the federal government will continue to do "everything possible to make sure the Gulf Coast recovers fully from this disaster."

"This road will not be easy, but we will continue to work closely with the people of the Gulf to rebuild their livelihoods and restore the environment that supports them," Obama said in a written statement. "My administration will see our communities, our businesses and our fragile ecosystems through this difficult time."

Deshamp said state waters of Mississippi reopened in mid-August and no oil is visible on the sand -- "But if you walk off in to the water, maybe ankle-deep, you're seeing tar balls all over the place."

"I think that's going to keep washing up for a long time to come," he said.

The Obama administration received its share of criticism for its handling of the spill. Republicans seized on the issue to compare its response to the Bush administration's disastrous handling of Hurricane Katrina, which struck the same region in 2005, while Democratic allies like Louisiana Sen. Mary Landrieu blasted the administration for halting offshore drilling until the cause of the disaster could be found.

Obama bluntly defended his response in a June interview, telling NBC he was on the case "before most of these talking heads were even paying attention to the Gulf." Asked about critics who considered his response too cerebral, Obama said he was consulting with experts "so I know whose ass to kick."

The cause of disaster remains under investigation by several arms of the U.S. government, including congressional committees, the Department of Justice and a Coast Guard-Interior Department panel that has held several rounds of hearings on the cause of the sinking.

BP shouldered some responsibility for the disaster after an internal investigation of the spill, but assigned much of the blame to contractors Halliburton, which cemented the well, and Transocean, which owned and operated the rig. Both Halliburton and Transocean sharply disputed the findings, arguing that BP's well design was at the root of the blowout.

The spill also put harsh new scrutiny on the Interior Department's regulation of offshore oil exploration, which had already been plagued by scandal in previous years.

The Minerals Management Service was split up into two separate agencies, one aimed at enforcing regulations and another that collected revenues. Its director at the time, Elizabeth Birnbaum, announced her resignation in May, though two sources told CNN she had been fired.

And the government was criticized for its early estimates of the spill, which were much lower than scientists eventually agreed was flowing. And while government scientists have estimated that 74 percent of the oil has either evaporated, been broke up or was skimmed or burned off, other researchers say much of the oil may have settled to the floor of the Gulf.

Those reports worry people like St. Pierre, who said BP needs to keep close tabs on the marine environment in the years to come.

"Time will tell. Let's see next year," he said. "I just hope we're not left alone."