DC is way out front in pop density. NY is 12th and Cali is 17th as of 2015.
the issue is city density, not state density ...
https://en.wikipedia.org/wiki/List_of_United_States_cities_by_population_density
There are the cities.
It’s pointless to look at population density for a STATE. The vast majority of California is empty space. The same is true for New York State. DC is a metro area with almost no empty space.
You want to look at cities or metro areas.