Portland's demonstration for the Global Climate Strike drew thousands of people.
Students left schools in events around the world to take part and direct attention to climate change.
In Portland, they started with a rally near Portland City Hall and then they marched across the Hawthorne Bridge. There were so many people they covered the entire length of the bridge.
Portland Police say one person was arrested on the bridge for vandalism. A small number of people in a nearby demonstration were wearing masks with hats that had the symbol for Antifa. Police confronted them, but no problems were reported.
After crossing the Hawthorne Bridge the group continued to rally outside of the Oregon Museum of Science and Industry.