Underwood-Petersville, Alabama  Underwood-Petersville is a census-designated place (CDP) in Lauderdale County, Alabama United States. It is part of the Florence - Muscle Shoals Metropolitan Statistical Area known as "The Shoals". As of the 2010 census, the population of the CDP is 3,247. Underwood-Petersville is located at (34.872469, -87.692776). According to the U.S. Census Bureau, the CDP has a total area of , all land. At the 2000 census there were 3,137 people, 1,295 households, and 953 families in the CDP. The population density was 520.5 people per square mile (200.9/km²). There were 1,378 housing units at an average density of 228.6 per square mile (88.2/km²). The racial makeup of the CDP was 94.68% White, 4.11% Black or African American, 0.19% Native American, 0.35% Asian, 0.10% from other races, and 0.57% from two or more races. 0.54% of the population were Hispanic or Latino of any race. Of the 1,295 households 30.2% had children under the age of 18 living with them, 60.1% were married couples living together, 9.7% had a female householder with no husband present, and 26.4% were non-families. 23.2% of households were one person and 9.3% were one person aged 65 or older. The average household size was 2.42 and the average family size was 2.84. The age distribution was 22.4% under the age of 18, 8.0% from 18 to 24, 28.2% from 25 to 44, 25.7% from 45 to 64, and 15.7% 65 or older. The median age was 40 years. For every 100 females, there were 98.4 males. For every 100 females age 18 and over, there were 95.6 males. The median household income was $37,159 and the median family income was $45,212. Males had a median income of $35,301 versus $21,129 for females. The per capita income for the CDP was $17,461. About 8.4% of families and 12.2% of the population were below the poverty line, including 19.8% of those under age 18 and 9.4% of those age 65 or over.