 As of the census of 2010, Plano had 259,841 people, 99,131 households and 69,464 families, up from 80,875 households and 60,575 families in the 2000 census.The population density was 3,629.1 people per square mile (1,400.8/km2).There were 103,672 housing units at an average density of 1,448.6 per square mile (559.3/km2).