The 11th annual 2023 (San Francisco) North Bay Science Discovery Day – a free public science festival to spark young people’s curiosity and wonder for science, technology, engineering, and mathematics (STEM) – was held on March 11, 2023 at the Sonoma County Fairgrounds. We estimate attendance between 8,000—10,000 attendees (even with rain!) participating in 100 hands-on STEM activities offered by 70 organizations.