This year the parade merged with the national Support Science march.
At the event in Nashville, Tennessee, where marchers shouted "science, not silence", lawyer Jatin Shah brought his sons, a 5-year-old who wants to be a dentist and 6-year-old who plans to be a doctor.
For example, the White House proposed significant cuts last month to federal agencies that fund scientific research, such as the National Institute of Health, NASA and the Environmental Protection Agency.
Organizers of the march encouraged scientists in their ranks to wear their lab coats, goggles, stethoscopes, field gear and other work clothes to make their presence known among a group that frequently shies away from public political displays.
"I thought, what if everyone who felt like me - who felt very disheartened and anxious and angry and fearful - what if we all took those feelings and channeled them into something positive?", Hyndman said via phone.
Despite saying the march was not partisan, Holt acknowledged it was only dreamed up at the Women's March on Washington, a day after Trump's inauguration on January 20.
The march itself is now scheduled for 2 PM EDT, from Constitution Avenue to Union Square in Capitol Hill.
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"Science should neither serve special interests nor be rejected based on personal convictions", it continues.
Brazil, Canada, many European nations, Japan, Mexico, Nepal, Nigeria and South Korea are all also planning science marches.
"They're targeting the Trump administration and they're saying that any politician who tries to undermine science, ruin trust in science, or politically motivate funding of science, particularly climate change, is a risk and they want to speak out against that". His entire research team is going to Saturday's March for Science. In Berlin, several thousand people participated in a march from one of the city's universities to the landmark Brandenburg Gate.
The march comes as many Americans are pessimistic about the environment.
"We need to stop and recognize the significance of science and the importance of funding it properly and using the evidence that it produces as the basis of good public policy", Associate Professor Stuart Khan and organizer at the Sydney march told ABC Australia.
Supporters gathered outside the Science Museum in Kensington, bearing placards on which double helices and chemical symbols sat alongside political slogans.
Protesters were to march to the US Capitol later in the day to carry their pro-science message. "That is a pretty serious attack not on just science but just on being human".