Facts:

– DC shouldn’t really count since it’s a single county (and yet
somehow California slightly edges it out), so I’ve included the specific
value for third-place Massachusetts, which as you can see is
significantly lower than the top two.

– Hawaii has five counties,
but of these, Kalawao County has a population of just 90 people – the
second-smallest in the country (after Loving County, TX which has 78)!
If this county were incorporated into the remainder of its island,
Hawaii’s average county population would jump from the present 286,000
to 358,000.

– Arizona may seem an outlier as it ranks fourth with
an average county population of 455k – higher than New Jersey and
Connecticut. It, like Nevada, has relatively few counties (15 vs 17) for
a geographically large state. However its average is more than 2.5
times as high as its neighbor to the northwest due to it having a much
higher population than the other low-density states of the region –
Nevada, Utah, and New Mexico all have somewhere between two and three
million people, whereas Arizona has nearly seven million. Contrast this
with Colorado with some 5.5 million but 64 counties, resulting in a far
lower average.

https://www.reddit.com/user/Mainstay17