--- title: Deepwater Horizon Oil Spill: 5 Years Later, How It Happened description: The Deepwater Horizon spill started on April 20, 2010 canonical: https://time.com/3818144/deepwater-horizon-anniversary/ author: Lily Rothman article:opinion: false article:content_tier: free article:published_time: 2015-04-20T16:00:37.000Z article:modified_time: 2026-02-22T06:19:22.815Z article:section: History og:title: Deepwater Horizon Oil Spill: 5 Years Later, How It Happened og:description: The Deepwater Horizon spill started on April 20, 2010 og:url: https://time.com/3818144/deepwater-horizon-anniversary/ og:site_name: TIME og:image: https://static.time.com/v3/assets/bltea6093859af6183b/bltc6d2c99aa18479a4/6987eaa455a859c231a89856/1101100517_400.jpg?branch=production&width=828&quality=75&auto=webp&crop=16:9 og:image:width: 1200 og:image:height: 675 og:image:alt: Big Spill og:type: article twitter:card: summary_large_image twitter:title: Deepwater Horizon Oil Spill: 5 Years Later, How It Happened twitter:description: The Deepwater Horizon spill started on April 20, 2010 twitter:image: https://static.time.com/v3/assets/bltea6093859af6183b/bltc6d2c99aa18479a4/6987eaa455a859c231a89856/1101100517_400.jpg?branch=production&width=828&quality=75&auto=webp&crop=16:9 ---  # What Caused the Worst Oil Spill in American History ## Video: TIME Explains: Challenges to America's Energy Independence [Watch (HLS stream): TIME Explains: Challenges to America's Energy Independence](https://cdn.jwplayer.com/manifests/DqaAia9D.m3u8) (1:29)  _Published 2013-10-10. The U.S. has been chasing energy independence for years, but even though new technology might make it possible, the situation is more complex than it appears. TIME's Bryan Walsh explains why._  by [Lily Rothman](https://time.com/author/lily-rothman/)  ## Lily Rothman Rothman is managing editor at TIME. Apr 20, 2015 4:00 PM UTC  The May 17, 2010, cover of TIME The May 17, 2010, cover of TIMECover Credit: PHOTOGRAPH BY CHRIS GRAYTHEN - GETTY IMAGES. INSET: AP  by [Lily Rothman](https://time.com/author/lily-rothman/)  ## Lily Rothman Rothman is managing editor at TIME. Apr 20, 2015 4:00 PM UTC Five years ago Monday, when there was an explosion on the Deepwater Horizon, an oil rig in the Gulf of Mexico, the first news reports said that nearly a dozen people had been killed by the blast. Before long, however, it was clear that the impact would continue to be felt, and by many more people. The oil spill that began that day and continued into the summer would end up being the worst such accident in U.S. history, spilling millions of gallons of crude into the fragile waterway. How it would be cleaned up remained a mystery, one that is still being answered today. Another mystery, as TIME’s Bryan Walsh explained in a cover story shortly after the spill began, was what had actually happened on that fateful day: --- > “” --- **_Read the full cover story, here in the TIME Vault:_** [The Big Spill](http://time.com/vault/issue/2010-05-17/page/1/) ```json [{"@context":"https://schema.org","@type":"NewsArticle","@id":"https://time.com/3818144/deepwater-horizon-anniversary/","mainEntityOfPage":{"@type":"WebPage","@id":"https://time.com/3818144/deepwater-horizon-anniversary/"},"headline":"What Caused the Worst Oil Spill in American History","datePublished":"2015-04-20T16:00:37.000Z","dateModified":"2026-02-22T06:19:22.815Z","description":"The Deepwater Horizon spill started on April 20, 2010","url":"https://time.com/3818144/deepwater-horizon-anniversary/","keywords":["Environment"],"thumbnailUrl":"https://static.time.com/v3/assets/bltea6093859af6183b/bltc6d2c99aa18479a4/6987eaa455a859c231a89856/1101100517_400.jpg?branch=production&width=1200&quality=75&auto=webp&crop=1200:675&height=675","author":[{"@type":"Person","name":"Lily Rothman","jobTitle":"Rothman is managing editor at TIME.","url":"https://time.com/author/lily-rothman/"}],"articleSection":"History","image":[{"@type":"ImageObject","url":"https://static.time.com/v3/assets/bltea6093859af6183b/bltc6d2c99aa18479a4/6987eaa455a859c231a89856/1101100517_400.jpg?branch=production&width=1200&quality=75&auto=webp&crop=1200:675&height=675","width":1200,"height":675,"headline":"Big Spill","caption":"Big Spill","creditText":"Cover Credit: PHOTOGRAPH BY CHRIS GRAYTHEN - GETTY IMAGES. 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