Thousands of people sporting patriotic costumes and toting hand-penned signs took a peaceful stroll in San Francisco under bright, clear skies Sunday afternoon to call for the impeachment of President Trump.

The crowd gathered at Justin Herman Plaza at 1 p.m. for speeches and then marched along the waterfront toward Fisherman’s Wharf while throngs of curious tourists looked on from sidewalks and cafes, many cheering support. After less than two hours, the protest was over, and the crowd dispersed, leaving behind three naked men standing in the plaza, the word “Trump” penned on their rumps.

The march was organized by several organizations, including Progressive Democrats of America, which said Trump’s firing of FBI Director James Comey is just one of many actions that collectively mean Congress should seriously look into tossing the president out of office. It was one of many such protests across the country and around the world Sunday.

Nearly everyone carried a sign, many calling for impeachment and several insisting that Trump release his tax returns. Others questioned his relationship with Russia, including one protester who wanted the president to “show us your rubles.”

One man dressed in Uncle Sam gear with blue sparkly shoes and a cotton beard glued to his chin. He carried sign reading, “Trump redefines the bully pulpit.”

“I feel like I need to be visible in my opposition to pretty much everything Trump is doing,” said the marcher, 48-year-old Daniel Johnson of San Francisco. “I want to be one of the people that can at least say, when everything goes south, I stood up, I did something.”

Johnson called Trump “reprehensible, callous, mean and unconcerned.”

March organizers pointed to more than 1 million signatures on the site www.impeachdonaldtrumpnow.org as backing for their sentiment, and those who showed ranged across all ages and ethnicities — though it appeared few conservatives were pitching in. The mood was defiant but festive, and after reaching Battery Street, the throng turned around and headed back to Justin Herman Plaza.

Debra Stein sat on the steps as the protest wrapped up, a bright orange sign on her lap that showed a glitter-covered image of a peach with Trump-like hair. The sign’s edges were adorned with pom-poms.

“I just want to get Trump out of office,” she said. “It’s time to get him out.”

Stein, like many of the marchers, said gathering with like-minded people is empowering.

Like-minded 6-year-old Ian Lee of San Francisco wore a Captain America T-shirt and toted a sign reading, in a shaky child’s handwriting, “Impeach Donald Trump.”

He said he has friends at his school who are from different countries and are worried about what might happen to them under Trump’s efforts to clamp down on immigration, and he didn’t like that.

“I just don’t like Donald Trump,” Ian said. “He does bad stuff.”

Chronicle staff writer Kevin Fagan contributed to this report.

Jill Tucker is a San Francisco Chronicle staff writer. Email: jtucker@sfchronicle.com Twitter: @jilltucker