They were each ordered to pay $75 (Ђ64) in fines and court costs, but Sheehan's lawyer said he plans to appeal the verdict.
All the defendants contended they were trying to deliver petitions to the White House calling for an end to the war in Iraq on Sept. 26, but found no one willing to accept them.
"Our petitions were rejected like every request I have made of the president has been rejected," Sheehan said.
Sheehan, 48, of Berkeley, California, has tried repeatedly to meet with President George W. Bush since her 24-year-old son, Casey, was killed in Iraq last year. She spent several weeks near the president's Crawford, Texas, ranch this summer, and plans to return there Thanksgiving week.
The defendants were among 300 people arrested by U.S. Park Police after they spent more than an hour on the Pennsylvania Avenue sidewalk north of the Executive Mansion. While some sat on the sidewalk, others chanted and sang songs. They were taken into custody after refusing police orders to leave.
Sheehan said she plans to take her peace activist message to Europe next month with stops in London and Madrid, reported AP. P.T.