With dark soil free from stones, farming was an early industry. The chief crop was hay, and raising sheep became a common occupation. In addition, there were 5 sawmills which manufactured long and short lumber, as well as specialty products like wooden bowls. In 1870, the population was 931.
Formerly possessing an independent public school department, Peru joined Maine School Administrative District 21 in 2006.
There were 585 households out of which 35.0% had children under the age of 18 living with them, 63.8% were married couples living together, 5.6% had a female householder with no husband present, and 25.3% were non-families. 19.8% of all households were made up of individuals and 7.9% had someone living alone who was 65 years of age or older. The average household size was 2.59 and the average family size was 2.98.
In the town the population was spread out with 26.7% under the age of 18, 5.8% from 18 to 24, 28.2% from 25 to 44, 24.2% from 45 to 64, and 15.1% who were 65 years of age or older. The median age was 40 years. For every 100 females there were 99.9 males. For every 100 females age 18 and over, there were 99.8 males.
The median income for a household in the town was $38,083, and the median income for a family was $43,047. Males had a median income of $32,171 versus $23,214 for females. The per capita income for the town was $16,383. About 3.4% of families and 6.0% of the population were below the poverty line, including 3.8% of those under age 18 and 7.0% of those age 65 or over.