Altoona is a city in Blair County, Pennsylvania, United States. The population was 43,963 at the time of the 2020 census. It is the princip…Altoona is a city in Blair County, Pennsylvania, United States. The population was 43,963 at the time of the 2020 census. It is the principal city of the Altoona metropolitan area, which includes all of Blair County and was recorded as having a population of 122,823.