(Washington, DC)  --  Four Oregon mayors are attending this year's winter meeting of the U.S. Conference of Mayors, which begins today in the nation's capital.  Charlie Hales of Portland, Denny Doyle of Beaverton, John Cook of Tigard, and Shane Bemis of Gresham are among the nearly 300 mayors engaging with Obama administration officials and congressional leaders during the three-day convention.  Six Washington mayors, including Ed Murray of Seattle and David Condon of Spokane, will also attend.  Discussions will be held on the economic health of America's cities.