The Deepwater Horizon rig explosion and resulting oil spill spawned significant changes in the drilling industry, led to hundreds of lawsuits and numerous investigations, and caused economic harm to hundreds of thousands of people along the Gulf Coast.
Here's a look at what has happened to key individuals and activities in the year since the April 20, 2010 disaster in the Gulf of Mexico.
BP EXECUTIVES: Gaffe-prone CEO Tony Hayward was ousted from his job and replaced by American Bob Dudley, who took over the British company October 1. Hayward was transferred to a BP affiliate in Russia. Other top executives also left the company, including Chief Operating Officer Doug Suttles, senior vice president Kent Wells and former head of exploration and production Andy Inglis.
RIG KIN: Several families of the 11 men who died aboard the Deepwater Horizon are pressing legal claims against the companies involved. Transocean has settled with at least five families for as yet undisclosed amounts. BP hasn't settled with any, and many of the families say they have heard little to nothing from the company since the disaster.
SPILL CLAIMS: The US$20 billion (NZ$25.2b) fund set up by BP to compensate victims has doled out only about US$3.8 billion (NZ$4.8b) to roughly 176,000 claimants, and oil spill victims complain of a slow, cumbersome process. Claims czar Ken Feinberg has said he only expects about half the fund to be needed to pay everyone. He said he is processing claims as fast as possible.
LITIGATION: More than 300 lawsuits filed against BP and the other companies involved with the rig were consolidated in federal court in New Orleans. A trial set for February 2012 will assign percentages of fault to BP and the other companies. Under the Oil Pollution Act, BP's liability for economic damages such as lost wages would be capped at US$75 million. But BP has waived the cap and has already paid billions. Transocean is seeking to limit its damages. The April 20 anniversary is the deadline for people to file claims against Transocean for damages that may result from the trial.
RESPONDERS: As of last month, BP employees and contractors working the response totalled roughly 2000, according to company spokesman Scott Dean. There were 48,000 responders at the height of the spill. The Coast Guard still participates in the cleanup and recovery, but that's also been significantly reduced along with the amount of protective boom deployed in the water. Thad Allen, the retired Coast Guard admiral who was the Obama administration's point-person on the oil spill, is now a senior fellow at the Rand Corp.
GULF DRILLING: A deepwater drilling moratorium imposed after the disaster was lifted October 12, but no permits were approved until February 28. Operators must follow strict new rules and show they have the ability to contain a deepwater blowout.
THE GULF: An Associated Press survey of researchers shows scientists rating the health of the Gulf of Mexico as nearly back to normal a year after the spill. However, muting their optimism are significant declines in key health indicators such as the sea floor, dolphins and oysters. It will likely take years to assess the full environmental effects on the Gulf.
INVESTIGATIONS: A joint US Coast Guard-Bureau of Ocean Energy Management Regulation and Enforcement investigative panel is expected to release some preliminary findings in the coming days or weeks on the disaster's causes. BP and a presidentially appointed commission have released their own findings pointing to a cascade of technical and managerial failures. A government-sponsored investigation into the failure of the blowout preventer - a key device used to choke off deep sea spills - identified a design flaw that kept it from doing its job.
ANNIVERSARY: Transocean plans to fly relatives of the 11 dead to the disaster site on April 20. Space is limited to three people per family. The chopper will circle the site a few times and return to shore. Plans call for the families to then be flown from Louisiana to Houston for a private service. BP is not involved in that effort, though a spokesman says it is planning an event to mark the anniversary. Details haven't been released.