The land on which the borough currently sits was once part of the Depreciation Lands reserved for Revolutionary War veterans. The first landowners in the area were James Robinson and Hugh Henry Brackenridge, purchasing parcels in 1799 and 1792 respectively. At the time of its organization as a borough, Bellevue had exactly the minimum population for such a designation: 300 residents.
Residents of the area tried unsuccessfully to obtain improvements from Ross Township, but officials were opposed to development along Venango Trail (today Route 19). In response, Bellevue was incorporated as a borough independent of Ross on September 7, 1867. The name of the borough was chosen by J. J. East, a linguist and early resident of the borough, and means "beautiful view."
According to the United States Census Bureau, the borough has a total area of 1.1 square miles (2.8 km2), of which 1.0 square mile (2.6 km2) is land and 0.1 square miles (0.26 km2), or 9.09%, is water. Its average elevation is 997 feet (304 m) above sea level.
As of the census of 2000, there were 8,770 people, 4,389 households, and 1,953 families residing in the borough. The population density was 8,768.1 people per square mile (3,386.1/km²). There were 4,770 housing units at an average density of 4,769.0 per square mile (1,841.7/km²). The racial makeup of the borough was 72.36% White, 22.40% African American, 0.17% Native American, 0.65% Asian, 0.16% from other races, and 1.25% from two or more races. Hispanic or Latino of any race were 3.81% of the population.
There were 4,389 households out of which 19.8% had children under the age of 18 living with them, 30.6% were married couples living together, 11.0% had a female householder with no husband present, and 55.5% were non-families. 48.1% of all households were made up of individuals and 13.4% had someone living alone who was 65 years of age or older. The average household size was 1.97 and the average family size was 2.92.
In the borough the population was spread out with 19.5% under the age of 18, 8.9% from 18 to 24, 35.0% from 25 to 44, 20.6% from 45 to 64, and 16.0% who were 65 years of age or older. The median age was 37 years. For every 100 females there were 80.7 males. For every 100 females age 18 and over, there were 76.9 males.
The median income for a household in the borough was $31,481, and the median income for a family was $42,382. Males had a median income of $30,683 versus $26,596 for females. The per capita income for the borough was $19,246. About 7.8% of families and 18.3% of the population were below the poverty line, including 11.2% of those under age 18 and 9.7% of those age 65 or over.
After the end of Prohibition, Bellevue opted to remain a "dry" town, meaning that the sale of alcohol in stores or restaurants is legally restricted by the Pennsylvania Liquor Control Board (PLCB). A referendum to overturn this status by allowing limited alcohol sales at certain establishments was included in the borough-wide primary elections, with voting held May 17, 2011. The referendum was defeated 849–761. Under state law, a similar referendum cannot be placed on the ballot again for at least four years.