Peru has the highest mean altitude of any town in the state. It lies on high ground in the Berkshire Hills, with three main peaks in the town. Much of Peru is forested, with a large portion of the northern third of town covered by a wildlife management area, and much of the southern third covered by the Peru and Middlefield State Forests. To the west of town, Ashmere Lake flows out into Bennett Brook, eventually reaching the East Branch of the Housatonic River. To the east of town, many brooks, including the Trout Brook, flow south and east towards the Westfield River (the Trout Brook is actually one of the main sources of the river).
Peru is bisected by Route 143, passing from east to west. No other state roads pass through the town. The nearest interstate, Interstate 90 (also known as the Massachusetts Turnpike), can be accessed approximately 20 miles away in Lee. The nearest bus and rail services can be found in Pittsfield, as can the closest regional airport (at Pittsfield Municipal Airport). The nearest national service can be found at Bradley International Airport in Windsor Locks, Connecticut.
As of the census of 2000, there were 821 people, 295 households, and 228 families residing in the town. The town is the ninth smallest of the 32 cities and towns in the county, and ranks 331st out of the 351 cities and towns in Massachusetts by population. The population density was 31.7 people per square mile (12.2/km²), ranking it 22nd in the county and 328th in the Commonwealth. There were 378 housing units at an average density of 14.6/sq mi (5.6/km²). The racial makeup of the town was 97.93% White, 0.24% African American, 0.12% Native American, 0.49% Asian, 0.12% from other races, and 1.10% from two or more races. Hispanic or Latino of any race were 0.12% of the population.
There were 295 households out of which 38.0% had children under the age of 18 living with them, 64.7% were married couples living together, 7.5% had a female householder with no husband present, and 22.7% were non-families. 16.3% of all households were made up of individuals and 5.1% had someone living alone who was 65 years of age or older. The average household size was 2.78 and the average family size was 3.14.
In the town the population was spread out with 27.8% under the age of 18, 6.0% from 18 to 24, 31.1% from 25 to 44, 27.4% from 45 to 64, and 7.8% who were 65 years of age or older. The median age was 37 years. For every 100 females there were 107.3 males. For every 100 females age 18 and over, there were 113.3 males.
The median income for a household in the town was $44,531, and the median income for a family was $51,071. Males had a median income of $35,469 versus $30,625 for females. The per capita income for the town was $18,636. About 4.1% of families and 4.9% of the population were below the poverty line, including 7.3% of those under age 18 and 2.7% of those age 65 or over.
On the state level, Peru is represented in the Massachusetts House of Representatives by the Second Berkshire district, which covers central Berkshire County, as well as portions of Hampshire and Franklin Counties. In the Massachusetts Senate, the town is represented by the Berkshire, Hampshire and Franklin district, which includes all of Berkshire County and western Hampshire and Franklin Counties. The town is patrolled by the Fourth (Cheshire) Station of Barracks "B" of the Massachusetts State Police.
On the national level, Peru is represented in the United States House of Representatives as part of Massachusetts's 1st congressional district, and has been represented by John Olver of Amherst since June 1991. Massachusetts is represented in the United States Senate by senior Senator Ted Kennedy and junior Senator John Kerry.
The nearest community college is Berkshire Community College in Pittsfield. The nearest state college is Massachusetts College of Liberal Arts in North Adams, and the nearest state university is the University of Massachusetts Amherst.