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:
I did RAGBRAI a couple of years ago with a friend! It was really fun and I recommend it to people all the time. My favorite memory was a guy running a slip n slide in his front yard, offering free jello shots to everyone who went down it.
That said, I'm not sure I'd do it again. The days (and especially the food) felt very same-y by the end of the week.