Near the American Association for the Advancement of Science annual meeting in Boston, researchers rallied behind science, the Associated Press and others report.
"We're really trying to send a message today to Mr. Trump that America runs on science, science is the backbone of our prosperity and progress," Geoffrey Supran, a postdoc at Harvard University and MIT, tells the AP.
Researchers have been particularly concerned about the new administration's stances on climate change, ability of government researchers to speak about their work, and "alternative facts."
"We know the playbook, but this is a different sport. We've seen that President Trump isn't going to respect scientists," adds Gretchen Goldman from the Union of Concerned Scientists at the New Scientist.
The Rally to Stand up for Science was organized by climatetruth.org and the Natural History Museum and endorsed by a number of national and regional scientific organizations, New Scientist adds. It notes that there was also a session at the conference itself devoted to scientific integrity and defending science during the Trump administration that was standing room only.
However, some researchers worry that such demonstrations might harm the scientific endeavor.
"To have science represented as this political force I think is just extraordinarily dangerous," the University of Maryland's Jim Gates tells the Guardian, noting that protestors appear to lack an end goal.
"At least as far as I can detect, there is no theory of action behind this," he says. "This bothers me tremendously.