This is an annual cross-state ride called RAGBRAI. It's been going for 52 years now. Riders typically use support teams, but I ride self-supported from the center of the state, ride half the route, and ride home. More photos:
My grandparents were on the first 25 or 30 RAGBRAIs. The year I was supposed to go was the first year they missed :( I hope you had a blast.