As of the census of 2000, there were 23,906 people, 11,134 households, and 6,045 families residing in the city. The population density was 4,097.0 people per square mile (1,583.2/km²). There were 12,802 housing units at an average density of 2,194.0/sq mi (847.8/km²). The racial makeup of the city was 86.28% White, 10.71% African American, 0.13% Native American, 0.28% Asian, 0.05% Pacific Islander, 0.61% from other races, and 1.92% from two or more races. Hispanic or Latino of any race were 1.59% of the population. 23.8% were of German, 10.0% Italian, 9.2% Irish, 7.7% Polish, 7.2% Slovak and 5.7% American ancestry according to Census 2000.
There are 11,134 households of which 22.4% have children under the age of 18 living with them, 34.1% were married couples living together, 15.7% had a female householder with no husband present, and 45.7% were non-families. 41.5% of all households were made up of individuals and 19.3% had someone living alone who was 65 years of age or older. The average household size was 2.11 and the average family size was 2.87.
Within the city, the population is spread with 21.3% under the age of 18, 7.9% from 18 to 24, 25.8% from 25 to 44, 23.0% from 45 to 64, and 22.1% who were 65 years of age or older. The median age was 42 years. For every 100 females there were 84.4 males. For every 100 females age 18 and over, there were 80.2 males.
The median income for a household in the city was $20,595 and the median income for a family was $28,279. Males had a median income of $26,163 versus $19,791 for females. The per capita income for the city was $13,236. 24.6% of the population and 18.9% of families were below the poverty line. Of the total population, 37.5% of those under the age of 18 and 12.6% of those 65 and older were living below the poverty line.
The main highway connecting Johnstown to the Pennsylvania Turnpike is US 219. In addition, there is also State Route 56, which is an expressway from 219 until Walnut Street. From there, it provides a connection to US 22 to the north of Johnstown, which connects to Pittsburgh and Altoona.
The local airport is the John Murtha Johnstown-Cambria County Airport and is served by United Airlines.
Passenger rail service is provided by Amtrak's daily 'Pennsylvanian'. The city is located on the former mainline of the Pennsylvania Railroad. Norfolk Southern operates (60-80) trains daily on these rails.
CamTran operates the local bus service, and the Johnstown Inclined Plane.