Butler County is a county in the Commonwealth of Pennsylvania. As of the 2020 census, the population was 193,763. Its county seat is Butler. Butler County was created on March 12, 1800, from part of Allegheny County and named in honor of General Richard Butler, a hero of the American Revolution. The county is part of the Greater Pittsburgh region of the …Butler County is a county in the Commonwealth of Pennsylvania. As of the 2020 census, the population was 193,763. Its county seat is Butler. Butler County was created on March 12, 1800, from part of Allegheny County and named in honor of General Richard Butler, a hero of the American Revolution. The county is part of the Greater Pittsburgh region of the state.