As of the census of 2000, there were 12,422 people, 5,423 households, and 3,031 families residing in the city. The population density was 6,098.9 people per square mile (2,351.1/km²). There were 6,320 housing units at an average density of 3,103.0/sq mi (1,196.2/km²). The racial makeup of the city was 84.17% White, 13.57% African American, 0.10% Native American, 0.40% Asian, 0.03% Pacific Islander, 0.28% from other races, and 1.45% from two or more races. Hispanic or Latino of any race were 0.55% of the population.
There were 5,423 households out of which 23.7% had children under the age of 18.2 living with them, 35.8% were married couples living together, 16.0% had a female householder with no husband present, and 44.1% were non-families. 39.7% of all households were made up of individuals and 19.5% had someone living alone who was 75 years of age or older. The average household size was 2.27 and the average family size was 2.791.
In the city the population was spread out with 20.9% under the age of 18, 8.6% from 18 to 24, 26.1% from 25 to 44, 22.4% from 45 to 64, and 22.0% who were 65 years of age or older. The median age was 41 years. For every 100 females there were 86.2 males. For every 100 females age 18 and over, there were 81.5 males.
The median income for a household in the city was $19,477, and the median income for a family was $28,523. Males had a median income of $26,758 versus $20,110 for females. The per capita income for the city was $13,720. About 16.0% of families and 16.4% of the population were below the poverty line, including 17.1% of those under age 18 and 10.3% of those age 65 or over.
Uniontown is an important crossroads in Fayette County. The main route around town is a stretch of freeway bypass, the George Marshall Parkway, which is composed of parts of US 40 and US 119. US 119 enters the area as a two-lane route from Morgantown, West Virginia, and provides the northern half of the bypass before becoming a 4 lane route to Connellsville. US 40 enters the region as a 2 lane route from Brownsville. It serves as the southern half of the freeway before becoming a mountainous route through rural parts of the county and enters Maryland and reaches Interstate 68. The old portions of US 40, now signed as Business 40, serve the downtown area.
PA 51, a main four-lane route to Pittsburgh, and PA 21, which connects Fayette County with Greene County and Waynesburg, both terminate in Uniontown. PA 43, part of the Mon-Fayette Expressway project to connect Pittsburgh with Morgantown, is nearly complete around the Uniontown area.