Marchers gather in Pershing Square in downtown Los Angeles for the March for Science.
Some 50,000 people signed up online to participate in the March for Science in Los Angeles, but event organizers estimate that more people are actually in attendance.
Marching in San Francisco
People listen to a pre-march talk near the Ferry Building ahead of the March for Science in San Francisco.
In New York City, the NYPD estimated that 40,000 people took place in the March for Science.
Marchers represented a variety of scientific interests, ranging from medical science to ocean science.
Famous scientists were honored during the March for Science in Washington, D.C.
No Planet B
A man dressed as an astronaut holds up a sign at the March for Science in Boston.
Make America think again
"As a child, I learned that we did not inherit this planet from our parents. We are borrowing it from our children, and I am marching here today to make sure my children and my children's children have an Earth. To protect it," Linda Montaquila, 55, a construction lawyer from Jupiter, Florida, told Live Science. Montaquila took part in the March for Science in Washington, D.C.
Marchers pose with their signs for the March for Science in Washington, D.C.
Participants gather on the National Mall for the rally before the March for Science in Washington, D.C.
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Denise Chow was the assistant managing editor at Live Science before moving to NBC News as a science reporter, where she focuses on general science and climate change. Before joining the Live Science team in 2013, she spent two years as a staff writer for Space.com, writing about rocket launches and covering NASA's final three space shuttle missions. A Canadian transplant, Denise has a bachelor's degree from the University of Toronto, and a master's degree in journalism from New York University.