Protesters in New York City and Washington, D.C. joined with demonstrators in other cities Saturday to march against President Trump one day after his inauguration.

Estimates of the crowd in the nation's captial were in the hundreds of thousands as the protest there swelled beyond its expected size.

"I think we're sending a message that we're powerful, we're worthy, and we're not just going to sit by idly while rights get taken away," one protestor said. "We're going to have each other's backs."

Seas of people blocked traffic as they marched from the National Mall.  On one street, a police car trying to move got stuck in the crowd. Marchers surrounded a float that had several supporters of President Trump on board and chanted, "Shame."

Other marchers shouted, "Black lives matter" and "My body, my choice," as they moved along Pennsylvania Ave. towards the White House.

Organizers say the peaceful march aimed to promote equality, regardless of gender, sexual orientation, race, and religion in the wake of a Trump administration, which officially began Friday.

The march's main goal was to call for a greater female influence on the political world.  They were also protesting the administration's plans to defund Planned Parenthood.

There were early signs across Washington that Saturday's crowds could top those that gathered Friday to watch President Donald Trump's inauguration.

The march's National Park Service permit initially estimated a turnout of 200,000, but the District of Columbia's homeland security chief had predicted turnout would be higher.

Marchers said they were upset by what they have heard from Trump, including his stances on women, immigration, and the environment.

"I'm horrified by the disrespect for what our country stands for, the lies and the flagrant disregard for truth that this administration has shown itself willing to propagate," one protestor said.

"I am basically against everything Trump has said in his campaign: hateful speech against immigrants, women, Muslims, LGBT people," said another.

The Women's March on Washington did not have a main organization to credit as its founder.  Instead, it grew out of some Facebook posts from women who were deeply upset by Trump's election win and felt they needed to do something to respond.

"It's been so friendly, so peaceful, just people hugging each other and laughing and celebrating," said one protester. "Hopefully the powers that be will listen."

"The administration has been running over a majority of the American people," said another. "They do not have a mandate, but they are acting as though they do."President Trump got a view of the protesters from the window of his limo.

Trump's motorcade was on its way back to the White House from a prayer service when he passed several prominent groups of protesters.

As he crossed one intersection, cars started honking loudly.

Some of the protesters held up signs that likened women's rights to human rights. It's a nod to a famous speech that former Democratic presidential nominee Hillary Clinton gave in China as first lady.

Other signs read, "We stand with Planned Parenthood."

Among those expected to attend were America Ferrera, Katy Perry, Cher, Gloria Steinem, Chelsea Handler, Julianne Moore, Scarlett Johansson, Amy Schumer, Olivia Wilde, Debra Messing, and Zendaya.

In the afternoon, Madonna used several obscenities during a speech at the march to emphasize her opposition to Trump. Her comments were carried live on cable television.

Madonna said like-minded Americans need to join together to make it "through this darkness" and show that "we are not afraid, that we are not alone."

Thousands are participated in a sister march in New York City that passed by the president's New York home.

Protesters in the Women's March on New York City left from an area near the United Nations earlier in the day and made their way to Trump Tower.

They were planning to march right in front of the president's home, but police stopped them and cordoned off the street at 55th St.

Protestors then made a turn, went up Madison Ave. and made their way to East 57th St. to effectively surround the area near the tower on 5th Ave.

There was no traffic going up and down the street between East 57th St. to about a block past East 55th St.

NY1 was originally told about 76,000 people were expected in the city's march, but police on-scene said they believe there are many more people.

Some people in the crowd said the fight for equal rights for women hits home for them.

"I feel very strongly about not defunding Planned Parenthood, because I have been personally touched by needing the service by not having healthcare," one woman protestor said. "I actually went in and was diagnosed with cervical cancer, and so through that I was able to get the help I needed and get on-track with my health and have two beautiful daughters."

Thousands of people had gathered near the meeting point near the United Nations before the march began, with celebrities and public officials rallying the crowd.

Protestors were expected to march from the plaza around noon, but people had to wait for the OK to move forward.

It appeared that the huge numbers of people slowed down the beginning of the march.

People were supposed to march in waves, with registered groups heading out to Trump Tower first.

Instead, some began to get agitated, with some attendees chanting "Let's march, let's march!"

Many Hillary Clinton supporters were in the marching crowd, along with men.  Cynthia Nixon, Rosie Perez, and Whoopi Goldberg were among the celebrities attending.

People from outside the city, including from New Jersey, Massachusetts, and Connecticut, came to march with New Yorkers, intending to send a message to the new administration.

"We've had these issues for years and years and years, and I've always said we need to get out in the streets and be heard," said a protestor at the plaza.

"Don't take away my ACA!" some protestors chanted, referring to the beginning of the dismantling of the Affordable Care Act.

Getting to the Women's March on Washington and its sister events around the country has proved to be a challenge.

Before Trump's inauguration Friday morning, Metro subway officials said only two of its parking garages and lots were at more than 60 percent capacity.

Saturday, many garages and lots at the ends of subway lines were at or near capacity.

In New York, Greyhound had to scramble to get extra buses and drivers for the 3:45 a.m. departure to Washington after a crush of last-minute ticket purchases.

A spokeswoman said they ended up with a total of 18 extra buses, and some could not leave until 6:30 a.m. because there weren't enough drivers on site.

So many people have turned out for the Women's March in Chicago that organizers have cancelled their plans to march through the city's downtown.

Instead, they plan to extend the ongoing rally on the city's lakefront.

Organizers say far more people than they were initially expecting are at the demonstration in Grant Park along Lake Michigan, and overflow areas are being used.

They say the planned march through downtown Chicago had to be canceled due to public safety concerns, but that the rally has been extended until 12:30 p.m. Central time.

Protesters are still arriving at the rally, many with signs critical of Trump.

Officials in Chicago added trains to their Saturday morning schedule in anticipation of higher-than-usual ridership, but passengers are still reporting standing-room-only trains and crowded platforms.

Some trains were so full they were bypassing scheduled stops.

Thousands are gathered in spots around the world for related Women's Marches.

A couple hundred people rallied in the Czech capital of Prague on Saturday in support of the march.

In Wenceslas Square in freezing conditions, they waved the portraits of President Donald Trump and Russian leader Vladimir Putin, as well banners that read: "This is just the beginning."

"We are worried about the way some politicians talk, especially during the American elections," organizer Johanna Nejedlova said.

Similar rallies unfolded in London, Berlin, Rome and other cities.

In Copenhagen, Denmark, protesters in the march's trademark pink woolen hats met outside the U.S. Embassy. "An alternative to the growing hatred must be created," participant Sherin Khankan said.