The Huffington Post was launched on May 9, 2005, as a liberal/left commentary outlet and alternative to news aggregators such as the Drudge Report. On February 7, 2011, AOL acquired the mass marketHuffington Post for US$315 million, making Arianna Huffington editor-in-chief of The Huffington Post Media Group. In 2012, The Huffington Post became the first commercially run United States digital media enterprise to win a Pulitzer Prize.
In July 2012, The Huffington Post was ranked #1 on the 15 Most Popular Political Sites list by eBizMBA Rank, which bases its list on each site's Alexa Global Traffic Rank and U.S. Traffic Rank from both Compete and Quantcast.
The Huffington Post founded by Arianna Huffington in May 2005 and launched a few days later on May 9. It has an active community, with over one million comments made on the site each month.
Prior to The Huffington Post, Huffington hosted a website called Ariannaonline.com. Her first foray into the Internet was a website called Resignation.com which called for the resignation of President Bill Clinton and was a rallying place for conservatives opposing Clinton.
In August 2013 the website banned anonymous comments.
In approximately June 2008 the site launched its first local version, HuffPost Chicago. In June 2009 HuffPost New York was launched, followed shortly by HuffPost Denver which launched on September 15, 2009  and HuffPost Los Angeles. launched on December 2, 2009, 2011 saw three new regional editions: HuffPost San Francisco since July 12, 2011,HuffPost Detroit, launched on November 17, 2011, and HuffPost Miami, online since November 2011. The most recent addition is "HuffPost Hawaii," launched in collaboration with the all online investigative reporting and public affairs news service Honolulu Civil Beat on September 4, 2013.
The Huffington Post launched its first international edition, HuffPost Canada, on May 26, 2011. On July 6 of the same year, the Huffington Post UK launched its UK edition. On January 23, 2012, Huffington, in partnership with Le Monde and Les Nouvelles Editions Indépendantes, launched Le Huffington Post, and the launch of French-language edition is the first in a non-English speaking country. On February 8, another French language edition was launched in the Canadian province of Quebec. On May Day, a US-based Spanish-language edition launched under the name HuffPost Voces, replacing AOL's Hispanic news platform, AOL Latino. The following month an edition for Spain was announced, as well as one for Germany. On September 24, an Italian edition, L'Huffington Post, was launched, directed by journalist Lucia Annunziata in collaboration with the media company Gruppo Editoriale L'Espresso. On May 6, 2013, an edition for Japan was launched with the collaboration of The Asahi Shimbun, the first international edition in an Asian country. With the launch of Al Huffington Post there is a third francophone edition, this time for the Maghreb area. On October 10, Munich-based Huffington Post Deutschland has been put online in cooperation with the liberal-conservative magazine Focus, covering German-speaking Europe. On 29 January 2014, the Brazilian version was launched as Brasil Post, in partnership with Abril Group, the first ever in Latin America. In September 2014 Huffington Post announced they will launch in Greece, India, and introduce HuffPost Arabi, an Arabic version of the website.
In 2011, after its purchase by AOL, The Huffington Post subsumed many of AOL's Voices properties (including AOL Black Voices, which had originally independently established in 1995 as Blackvoices.com, and AOL Latino). The Voices brand was expanded in September 2011 with the launch of Gay Voices, a vertical dedicated to LGBT-relevant articles. Other established sections, such as Impact (launched in 2010 as a partnership between Huffington Post and Causecast), Women, Teen, College, Religion and the Spanish-language Voces (en español) are also sorted under the Voices meta-vertical.
By late 2013, however, The Huffington Post was taking steps to operate as more of a "stand-alone business" within AOL, taking control of more of its own business and advertising operations, and focusing efforts on "premium advertising".
In addition to columns by Arianna Huffington and a group of contributors such as John Conyers, Harry Shearer, Jeff Pollack, and Roy Sekoff, The Huffington Post has many bloggers—from politicians and celebrities to academics and policy experts—who contribute on a wide range of topics. Specialist contributors include spiritual author Craig Taro Gold and health expert Jeff Halevy.
Celebrities are allowed to post blogs on the site, and a number have opted to do so over the years. In many cases, such as that of Robert Reich, former Secretary of Labor, content is cross-posted among multiple sites.
The Huffington Post 's OffTheBus is a citizen-powered online news organization that is a collaboration between The Huffington Post, New York University (NYU), and Jay Rosen's NewAssignment.Net.The Huffington Post 's FundRace is a website that tracks contributions to the presidential campaigns and includes a mapping feature that shows contributions broken down by city, neighborhood, and block.
In August 2006, The Huffington Post announced that SoftBank Capital would invest $5 million in the site, which had grown in popularity in only a year, to help expand it. Plans included hiring more staff to update the site 24 hours a day, hiring in-house reporters and a multimedia team to make video reports. Alan Patricof's Greycroft Partners also invested. The news marked the site's "first round of venture capital funding".
The site has now invested in video blogging, with many of the site contributors contributing via video, capturing clips in the media and posting them on the site.
In November 2008, The Huffington Post completed $15 million fundraising from investors to finance expansion, including more journalism and the provision of local news across the United States.
On February 7, 2011, AOL announced it would acquire The Huffington Post for US$315 million. As part of the deal, Arianna Huffington became president and editor-in-chief of The Huffington Post Media Group, including The Huffington Post and existing AOL properties Engadget, TechCrunch, Moviefone, MapQuest, Black Voices, PopEater (now[when?] HuffPost Celebrity), AOL Music, AOL Latino (now HuffPost Voices), AutoBlog, Patch and StyleList.
The Huffington Post has been criticized by several science bloggers, as well as online news sources, for including articles by supporters of alternative medicine and anti-vaccine activists and for allegedly censoring rebuttals written by science bloggers before publishing them.
Dana Ullman, a notorious homeopathy apologist, actually has a regular blog over at HuffPo. For those of us who follow such things, the start of his blog there marked the point of no return for the Huffington Post – clearly the editors had decided to go the path of Saruman and "abandon reason for madness." They gave up any pretence of caring about scientific integrity and became a rag of pseudoscience.
In April 2011, The Huffington Post was targeted with a multimillion dollar lawsuit filed in United States District Court in New York by Jonathan Tasini on behalf of thousands of uncompensated bloggers. The suit was dismissed with prejudice on March 30, 2012 by the court, holding that the bloggers had volunteered their services, their compensation being publication.
Although Arianna Huffington has stated that her paper is "not positioned ideologically in terms of how we cover the news," representatives of the Republican Party have indicated that they believe The Huffington Post 's headline writers, bloggers, and commentators are hostile to their views and tend to negatively spin articles, and especially headlines, about Republican Party candidates. According to Michael Steel, press secretary for Republican Party House leader John Boehner, Republican aides "engage with liberal websites like The Huffington Post [anyway, if for] no other reason than [because] they drive a lot of cable coverage." Jon Bekken, journalism professor at Suffolk University, has cited The Huffington Post as an example of an "advocacy newspaper."Wall Street Journal columnist James Taranto mockingly calls it the "Puffington Host." 
In 2012, The Huffington Post won the Pulitzer Prize in the category of national reporting for senior military correspondent David Wood's 10-part series about wounded veterans, Beyond the Battlefield.
The Huffington Post is 2010 People's Voice Winner in the 14th Webby Awards and is the Winner in Lead411's New York City Hot 125. The Huffington Post lost the 2010 Webby Award jury prize for Best Political Blog to Truthdig.
The Huffington Post received a Peabody Award in 2010 for "Trafficked: A Youth Radio Investigation."
The Huffington Post was named second among the 25 Best Blogs of 2009 by Time.
The Huffington Post won the 2006 and 2007 Webby Awards for Best Politics Blog.
Huffington Post contributor Bennet Kelley was awarded the Los Angeles Press Club's 2007 Southern California Journalism Award for Online Commentary for political commentary published on the site.
The Huffington Post is ranked the most powerful blog in the world by The Observer.
The Huffington Post co-founder Arianna Huffington was named in 2009 as number 12 in Forbes ' first ever list of the Most Influential Women In Media. The same year, she was ranked as number 42 in The Guardian 's Top 100 in Media List.
^"Julie Gray". Huffington Post. Retrieved 1 August 2014. "A Hollywood refugee living in the Middle East, Julie Gray has authored two books and is working on a memoir. A former Hollywood story analyst who has taught at Warner Bros., Julie now works with entrepreneurs, writers and innovators world wide-to shape narrative, edit stories and bridge the gap between art and commerce."
^"Get Off the Bus : CJR". cjr.org. Retrieved March 7, 2009. "OffTheBus (OTB) was a citizen-powered campaign news site co-sponsored by The Huffington Post and Jay Rosen’s NewAssignment, at New York University’s Arthur L. Carter Journalism Institute."