As of the 2010 census, there were 579,999 people, 230,233 households, and 144,120 families residing in the city. The population density was 956.4 inhabitants per square mile (321.9/km²). There were 256,930 housing units at an average density of 375.9 per square mile (145.1/km²).
What was the density of the population per square mile?
{'text': '956.4', 'answer_start': 140}