Douglas's reading looks wrong, and this site says so rather than hide it
The radiance figure on file for Douglas is exactly 0.0, and a city of 15,819 people does not genuinely read zero light from orbit. That points to a sampling miss, the wrong coordinate, water, or unlit terrain right where the sample point landed, rather than an actual dark sky.
This is flagged instead of shown as a normal result because reporting it as "Douglas's dark sky" would be reporting a data error as a fact, see the data quality guide for how this gets checked.
The nearest reliable reading to Douglas
Sierra Vista, AZ is about 47 miles from Douglas and has a trustworthy reading: rural band. It's the closest usable stand-in until Douglas's own figure is corrected.
Because Douglas's own coordinate is what produced the bad reading, that distance figure is itself approximate, not a confirmed measurement.
Douglas against the rest of the dataset
Douglas, AZ has a population of about 15,819, one of 3,206 US cities in this dataset, 3,187 of which have a usable brightness reading today.