And since it also was Earth Day, signs bore these slogans: "Make Our Planet Great Again," "Protect Wild Utah" and "Save the Earth go Vegan."
Nickie Nelson carried a sign that read, "I Trust Science Not Trump."
"It's a reference to the administration and the president himself who says things that are demonstrably not factual," said Nelson, who had a 35-year career in the aerospace industry as a system engineer.
She said she attended the march to support science findings that are vetted by peers and published so others can critique them.
"There's just too many people these days that can't accept what's really happening in the world," Nelson said.
Naveen Nagarajan, a post-doctorate fellow at the Mario Capecchi Lab at the University of Utah, said he and others were rallying to defend funding for their genetic research.
Nagarajan said his research focuses on a gene primarily found in brain cells that controls the immune aspect of the nervous system. Research in mice suggests that the absence of the gene is linked to obsessive compulsive disorder in humans, he said.
"We are here for the march to support our community with the request that we need more funding to do our science," Nagarajan said.
While scientific progress is incremental, he said the hope for his research is that someday it might produce treatment for obsessive compulsive disorder and related behaviors.
Mario Capecchi, who won the Nobel Prize in Physiology and Medicine in 2007, was clearly the star of the Capitol steps rally, beginning his short speech as the crowd chanted "Mario, Mario."
After the sound system cut out for a short time, Capecchi cited a number of breakthroughs in medicine that treat common diseases and spoke about how science solves environmental problems.