Women by the thousands deliver rebuke to Trump, from Iowa to D.C.

Hundreds of thousands of women and supporters rallied Saturday in the nation's capital and in cities around the world to send a message of defiance and hope to President Donald Trump a day after he took office.

Organizers said half a million people — double earlier estimates — were thought to be attending the Women's March on Washington, with bigger-than-expected crowds in other cities, too.

What started as a Facebook post by a Hawaii retiree became a historic international rebuke of a new president that packed cities large and small — from Des Moines to Detroit, London to Los Angeles, and Paris to Park City, Utah.

Organizers planned more than 670 events nationwide and in another 70 cities around the world, including Tel Aviv, Barcelona, Mexico City, Berlin and Yellowknife in Canada's Northwest Territories.

In Chicago, after 150,000 demonstrators swamped downtown, officials canceled the march portion of the event.

The fear and anger among the demonstrators at Trump's rise to the most powerful position in the United States reverberated at renowned protest sites worldwide, from the Trocadero in Paris to Trafalgar Square in London.

Marina Knight, a 43-year-old executive assistant, and her 9-year-old daughter were two of the tens of thousands marching in London.

'It's the first time we felt it was vital to march,' Knight said. 'I feel the rights we take for granted could go backwards, and we owe it to our daughters and the next generation to fix this somehow.'

In Washington, protesters craned their necks to listen to the many speakers.

The crowd was so big that attendees began marching before the speakers were done. They paraded informally down Constitution Avenue, past the Washington Monument, a noisy procession broken with cheers and chants.

'As we walked, we chanted, 'This is what democracy looks like' and sang songs, said Betsy Kutter, 73, from Cedar Rapids, a retired reporter for The Gazette who participated.

Demonstrators carried a seemingly endless array of colorful signs bearing messages like 'My body, my choice,' 'Weak men fear strong women' and 'Michelle Obama 2020.'

The rallies were organized under the rubric of women's rights, which many fear are threatened by the administration.

But the march's platform also incorporated other progressive causes, such as health care, the environment, racial justice and abortion rights.

A sea of pink knitted hats — the movement's signature headgear — supplanted the red caps worn a day earlier by Trump supporters who had come to Washington for his inauguration.

'Yesterday was their day; today is ours,' said Kim Crawford of Clinton, Md. Of Trump, she said: 'I'm not sure he'll hear our voices, but we're raising them.'

Organizers and many of the marchers said they did not want the focus to be in opposition to the new president, but rather on the causes they sought to promote.

But disdain for Trump's past words and actions during a bitterly divisive campaign were on full display, and often reflected in signs that played off explicit language in a video in which Trump talked about sexually assaulting women.

Many said they were braced for an unraveling of freedoms they had come to take for granted.

'I'm pretty disheartened,' said Louise McAfee of New York, spurred by her concerns over health care. 'But I'm also pretty hopeful.'

While most of the marchers were women, men also turned out in considerable numbers. Jacob Osterman traveled from Boston to join in.

'Women are part of humanity, like all of us,' he said. 'How can anyone not understand that?'

The turnout for the Washington march was a show of force that gave signs of exceeding the attendance of the presidential inauguration a day earlier. Washington Metro trains that had been lightly used Friday were jammed so full of protesters with signs and pink hats Saturday that crowds on platforms had to wait for more trains.

'People are really frightened about losing their health insurance,' said Gretchen Stanford of Alexandria, Va. 'And frightened about lots of other things.'

Actress America Ferrera got the rally off to a rousing start, invoking her birth in Los Angeles to Honduran parents.

'It's been a heart-rending time to be both a woman and an immigrant. Our dignity, our character, our rights have been under attack,' she told the crowd. 'But the president is not America. We are America.'

Gloria Steinem, a longtime leader of the feminist movement, scorned the notion of male patriarchy, declaring, 'No more asking Daddy!' Actress Scarlett Johansson mounted a defense of Planned Parenthood, threatened with defunding under the new administration.

Singer Madonna swore on live TV while discussing Trump before singing her 1989 hit 'Express Yourself.' Cher appeared, as did former U.S. Secretary of State John Kerry, who waved to supporters as he walked his yellow, Labra.

Clinton tweeted her gratitude as the Washington rally got underway, telling them: 'Thanks for standing, speaking & marching for our values @womensmarch. Important as ever. I truly believe we're always stronger together.'

Trump, in a Twitter post Saturday, wrote, 'I am honored to serve you, the great American People, as your 45th President of the United States!' He made no mention of the protests.

The Los Angeles Times, the Washington Post, Reuters and The Gazette staff contributed to this report.