The RAGBRAI route from Cherokee to Lake City today goes through Sac City. It comes into from the north on M54, then goes west on US 20 through town until M54 turns south.
This is possibly the only time RAGBRAI has ever used a portion of US 20. It’s fitting/ironic, then, that the street in Sac City will cease to be 20 within the next two years. In fact, once that happens, Sac City will be the county seat most isolated from state-maintained roads.
Various sections of old 20 have been used quite often. The old alignments of all the major routes are sort of an inadvertent contribution from the state to the ride.