The closure of comes in the same week that MSNBC bought Everyblock.com and others predict potential millions to be made in the hyperlocal market.
A spokeswoman for the Washington Post, told the Loudoun Independent: "While the Washington Post remains dedicated to maintaining a high level of coverage of the counties surrounding Washington, DC, we found that our experiment with LoudounExtra.com as a separate site was not a sustainable model."
The Washington Post was one of the first of a number of media owners in the US to launch hyperlocal projects.
Earlier this year The New York Times launched The Local, AOL bought Patch.com and The Huffington Post also announced plans to launch local versions of its site.
These ventures joined a slew of start-up hyperlocal sites across the US including the likes of Baristanet, Brownstoner, Examiner.com, The San Diego News Network and theloopny.com.
The Washington Post said that LoudounExtra.com was likely to be turned off in September and content moved to Washingtonpost.com.
The closure looks almost certain to kill off any plans the paper had to rollout the site in other areas as the New York Times is considering. It wants to use the Local as a platform for bloggers across the US.
The Washington Post had planned another hyperlocal site extra site, Fairfaxextra.com, which failed to launch.
Last year the Wall Street Journal reported in a story headlined "Big Daily's hyperlocal flop" that almost a year after launch LoudounExtra.com was still searching for an audience and suffering the loss of its chief architect, Rob Curley.
Jim Brady, executive editor of Washingtonpost.com, told the WSJ at the time: "It's too early for us to put any kind of stamp on it as a success or failure. We're just going to keep experimenting."
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