In New York, protesters stretching at least eight blocks chanted: 'He cheats, he lies, open up your eyes' near the Trump International Hotel on the edge of Central Park.
'I think he's got a mean personality,' said marcher Edith Cresmer, a 78-year-old urban planner. 'But the worst thing about him is how he incited peoples' fears and pits them against each other.'
Luis Llobera, 38, and his wife and baby took a train from Westchester County north of the city attend the Trump protest.
'We are not American citizens but our son is,' he said as his wife cradled their 7-month-old, Atlas. 'We want to make sure our son has a government that is right and good.'
Los Angeles was the first protest organized under the hashtag. Activists there showed off their commitment to the cause by dressing up in costume to mock the president.
There were no arrests at the L.A. protest.
In downtown Chicago, about 1,200 people gathered across the Chicago River from the Trump International Hotel and Tower.