Centuries
This pages tracks progress riding a century (a 100-mile ride) in each of the 50 US states.
Done
Planned
The process of constructing the square state grid above taught me some great trivia about US geography.
For example, Minnesota is the northernmost state in the contiguous US by about 133 miles; I would have guessed Maine.
Washington is the westernmost (this is believable).
Removing the contiguity constraint, Alaska is the westernmost, northernmost, but also the easternmost, under the hemisphere definition, since the Aleutian Islands cross the anti-meridian.