Greta Thunberg made her way to the march shortly after it began at 12:45 pm on Broadway.
Then she brought out her hand-painted sign, which says "School strike for climate" in Swedish.
Before the march began, protesters gathered in Foley Square, many of them carrying replicas of Thunberg's sign.
Most signs expressed a sense of urgency. Some demonstrators climbed onto lampposts to get their message out.
Others gathered together in the grass, like the employees of Patagonia Sports in Manhattan.
Many of the demonstrators were young — some of them missed school to join the ranks.
Some signs focused on the environmental impacts of climate change.
Others blamed politicians, like this sign featuring President Trump and Senate Majority Leader Mitch McConnell.
Some protesters made signs to give away.
Others got creative with props.
Around 12:30 pm, the marchers moved from Foley Square down Broadway, toward Battery Park.
This sign features the eponymous characters from the TV show "Rick and Morty."
Some signs were simple and stark.
Others adapted meme culture for their message.
Signs weren't the only ways marchers supported the cause — some wore T-shirts.
This sign pointed out the effects of climate change on birds while having a sense of humor.
Some signs took humor to a new level.
But the overarching messages many demonstrators had was the importance of science — especially signs from student protesters.
