Most of Blue Grass is part of the Davenport–Moline–Rock Island, IA-IL Metropolitan Statistical Area, but the Muscatine County portion of the city is considered part of the Muscatine Micropolitan Statistical Area.
There were 443 households out of which 35.0% had children under the age of 18 living with them, 62.5% were married couples living together, 12.2% had a female householder with no husband present, and 21.4% were non-families. 16.9% of all households were made up of individuals and 6.1% had someone living alone who was 65 years of age or older. The average household size was 2.64 and the average family size was 2.95.
In the city the population was spread out with 25.1% under the age of 18, 8.0% from 18 to 24, 29.9% from 25 to 44, 27.4% from 45 to 64, and 9.7% who were 65 years of age or older. The median age was 37 years. For every 100 females there were 95.5 males. For every 100 females age 18 and over, there were 95.5 males.
The median income for a household in the city was $51,923, and the median income for a family was $55,208. Males had a median income of $37,135 versus $22,350 for females. The per capita income for the city was $20,811. About 3.8% of families and 4.9% of the population were below the poverty line, including 5.7% of those under age 18 and 4.3% of those age 65 or over.