The anti-war activist is running as an independent against House Speaker Nancy Pelosi, who has represented San Francisco in Congress since 1987.
"The country is ripe for a change," said Sheehan, who spoke at a podium with her son's photograph attached to it. "It's going to start right here and right now."
Sheehan's 24-year-old son, Casey, was killed in Iraq in 2004. Since then, she has gained international notoriety by setting up camp outside President Bush's Texas ranch and demanding to meet with the president.
Last month, she announced her intention to run against Pelosi if the speaker didn't move to impeach Bush by July 23. On Thursday, she said Pelosi had "protected the status quo" of the corporate elite and had lost touch with people in her district, most of whom, she said, want American troops out of Iraq.
Nadeam Elshami, a spokesman for Pelosi, said the speaker has always opposed the war in Iraq and has focused on bringing troops home "safely and soon."
He would not comment on Sheehan's candidacy.
Sheehan admitted she has no funds for a campaign, but planned to immediately get started raising money. Without giving further specifics, Sheehan said she wouldn't accept money from corporations and would run on a platform of universal health care. Sheehan said she also wants to make college affordable and improve ethics in the legislative and executive branches.
She also said the money being spent on the war in Iraq would be better spent domestically.
Daniel Ellsberg, the former high-level Pentagon analyst who in 1969 leaked the Pentagon Papers to Congress and the media, showed his support for Sheehan. Ellsberg was arrested twice with other protesters outside Bush's Texas ranch.
"At the moment, facing a well-funded, powerful incumbent without party support, the odds against Cindy appear insuperable," Ellsberg said. "But we plan to change that."