As of the census[15] of 2000, there were 120,293 people, 46,712 households, and 32,371 families residing in the county. The population density was 179 inhabitants per square mile (69 inhabitants/km2). There were 49,859 housing units at an average density of 74 units per square mile (29/km2). The racial makeup of the county was 93.13% White, 5.25% Black or African American, 0.11% Native American, 0.40% Asian, 0.02% Pacific Islander, 0.17% from other races, and 0.91% from two or more races. 0.67% of the population were Hispanic or Latino of any race. 37.7% were of German, 20.0% Irish, 14.9% Italian, 12.0% English, 6.4% American, 6.2% Polish, 3.7% Scotch-Irish, 3.3% Dutch ancestry.
There were 46,712 households, out of which 29.30% had children under the age of 18 living with them, 54.80% were married couples living together, 10.90% had a female householder with no husband present, and 30.70% were non-families. 27.00% of all households were made up of individuals, and 13.20% had someone living alone who was 65 years of age or older. The average household size was 2.44 and the average family size was 2.96.
In the county, the population was spread out, with 23.40% under the age of 18, 8.90% from 18 to 24, 26.10% from 25 to 44, 23.50% from 45 to 64, and 18.10% who were 65 years of age or older. The median age was 40 years. For every 100 females there were 94.70 males. For every 100 females age 18 and over, there were 90.80 males.
As of June 12, 2023, there are 70,553 registered voters in the county. Republicans hold a plurality of voters by a margin of 10,354 voters (14.67% of the total registered). There are 35,735 registered Republicans, 25,381 registered Democrats, 7,319 registered non-affiliated voters, and 2,118 voters registered to third parties.[19]
Mercer County was previously considered a political bellwether for the state of Pennsylvania since its demographics, urban-rural ratio, and party affiliation once closely mirrored the state as a whole. In 2000, Al Gore carried it against George W. Bush. This trend failed to hold true in 2004 and 2008, in which Mercer County voted more conservatively than the rest of the state. In 2004, Bush won Mercer County with 51% of the vote. That year, John Kerry won the state as a whole with 51% of the popular vote. In 2008, John McCain won Mercer County by fewer than 200 votes, as he and Barack Obama each received roughly 49% of the popular vote. Obama won Pennsylvania as a whole with 55% of the popular vote. Each of the three statewide office winners also carried Mercer in 2008. In 2016, Donald Trump won Mercer County by 12,403 votes, and he also won all of Pennsylvania. Each of the three Republican candidates for statewide office carried Mercer County in 2016. In 2020, Trump again carried the county, despite Pennsylvania narrowly voting for Joe Biden. Trump won 62% of the vote, the largest majority for any major party candidate since 1964, and the largest majority for a Republican since 1928.[citation needed]
The Wendell August Forge, the last remaining working forge in the state, was open to the public for tours, but it burned down on March 6, 2010.[22] It has since reopened in new facilities.
Mercer County Court House built in 1909.
Communities
Map of Mercer County, Pennsylvania with Municipal Labels showing Cities and Boroughs (red) and Townships (white)
Under Pennsylvania law, there are four types of incorporated municipalities: cities, boroughs, townships, and, in one case, towns. The following cities, boroughs and townships are located in Mercer County:
