"Grey's Anatomy" star Patrick Dempsey raised more than $1.1 million for cancer over the weekend when 4,000 people biked, walked, or ran in races through his hometown of Lewiston, Maine.

Proceeds from the second annual "Dempsey Challenge" will benefit the Patrick Dempsey Center for Cancer Hope and Healing at Central Maine Medical Center, built in Lewiston to honor his mother.

Dempsey created the Challenge to serve as the primary fundraising vehicle for the Dempsey Center, which provides free support, education and wellness services to cancer patients, survivors and caregivers. (Race Video below)

Thousands of spectators took advantage of the beautiful autumn weekend, enjoying a free, family-friendly Festival in the Park, which included a Health and Wellness Expo, Spirit of Hope tent for cancer survivors, KidZone, live entertainment, and a lobster bake.

Shortly after the crossing the finish line, Dempsey dismounted and joined his mother, Amanda, leading the crowd in a Cancer Survivor Walk. Handmade mile markers honored the memories of those impacted by cancer and 1,000 prayer flags containing messages of hope and inspiration were displayed along the way.

The 2-day event culminated onstage with an inspirational speech by Dempsey who expressed his gratitude to all involved. The actor founded the Center in March 2008, as a response to his mother's multiple battles with ovarian cancer.

WATCH a local news video from the race site–and LEARN more about the next race and see a photo of Dempsey with his mom at www.dempseychallenge.org.