Marshalltown, IA: how dark is the sky here?
Satellite radiance puts Marshalltown in the suburban band. Light dome dominates much of the sky. Only the brightest stars and planets stand out clearly. That's brighter than 68.5% of the 3,206 US cities in this dataset.
This comes from a satellite measuring light radiating upward, not a person's eyes on the ground, so it isn't the same as a Bortle class, though the two track each other closely.
How far Marshalltown is from a meaningfully darker sky
48 miles from Marshalltown, straight-line, sits Johnston, IA, the nearest city here with a darker sky than Marshalltown's own suburban band.
Johnston, IA is itself still a measured city, not a designated dark-sky park, this only compares against the 3,206 places this dataset covers.
How Marshalltown compares nationally
About 27,886 people live in Marshalltown, IA, sized enough to appear in this dataset of 3,206 incorporated US cities. Marshalltown places 2,185 of 3,206 cities in this dataset's darkest-to-brightest order.