Settled in 1762, it was incorporated on June 3, 1848 as Mansel, the name given the island by John Winthrop's company of emigrants to the Massachusetts Bay Colony in 1630.
Two months later, on August 8 it was renamed Tremont, which means "three mountains" in French. By 1880, when the population was 2,011, the town had a sawmill, shipyard, gristmill, shingle mill and brickyard. Fishing and fish curing were the principal industries. Today, tourism is important to the economy.
According to the United States Census Bureau, the town has a total area of 52.4 square miles (136 km2), of which, 16.9 square miles (44 km2) of it is land and 35.5 square miles (92 km2) of it (67.84%) is water. Located on southwestern Mount Desert Island, Tremont is beside Blue Hill Bay and the Atlantic Ocean.
The town is crossed by state routes 102 and 102A. It borders the towns of Mount Desert to the north and Southwest Harbor to the east.
As of the census of 2000, there were 1,529 people, 662 households, and 436 families residing in the town. The population density was 90.7 people per square mile (35.0/km²). There were 1,075 housing units at an average density of 63.8 per square mile (24.6/km²).
The racial makeup of the town was 98.04% White, 0.33% African American, 0.65% Native American, 0.26% Asian, 0.07% from other races, and 0.65% from two or more races. Hispanic or Latino of any race were 0.33% of the population.
There were 662 households out of which 28.2% had children under the age of 18 living with them, 54.8% were married couples living together, 7.9% had a female householder with no husband present, and 34.0% were nonfamilies. 25.4% of all households were made up of individuals and 8.5% had someone living alone who was 65 years of age or older.
The average household size was 2.31 and the average family size was 2.76. In the town the population was spread out with 22.8% under the age of 18, 4.9% from 18 to 24, 28.4% from 25 to 44, 28.7% from 45 to 64, and 15.2% who were 65 years of age or older.
The median age was 42 years. For every 100 females there were 89.9 males. For every 100 females age 18 and over, there were 86.1 males. The median income for a household in the town was $36,750, and the median income for a family was $43,472. Males had a median income of $28,026 versus $21,835 for females.
The per capita income for the town was $19,420. About 5.0% of families and 7.4% of the population were below the poverty line, including 8.7% of those under age 18 and 8.0% of those age 65 or over.