Butler County, Pennsylvania, was created on March 12, 1800, from a portion of Allegheny County. Like many other Western Pennsylvania counties, Butler County was named for a Revolutionary War hero, General Richard Butler.

Some famous inventions and discoveries were made in Butler County. Saxonburg was founded as a Prussian colony by John A. Roebling, a civil engineer, and his brother Carl. After farming for a time, Roebling returned to engineering, and invented his revolutionary "wire rope.", which he first produced at Saxonburg. He moved the operation to Trenton, New Jersey. He is best known for designing his most famous work, the Brooklyn Bridge, but designed and built numerous bridges in Pittsburgh and other cities as well.

At what is now known as Oil Creek, Butler County resident William Smith and Edwin Drake first proved oil could be tapped from underground for consistent supply. The Jeep was developed in Butler County by American Bantam in 1941.

Famous politicians have lived in and traveled through Butler County. U.S. Senator Walter Lowrie, the only senator from Butler, built a home in 1828 that still stands behind the Butler County Courthouse. The house has been adapted for use by the Butler County Historical Society. Butler's highest-ranked federal official is William J. Perry, Secretary of Defense under President Bill Clinton from 1994 to 1997. He graduated from Butler High School in 1945.

George Washington passed through this area during the French and Indian War. In 1923, the funeral train of President Warren G. Harding passed through Butler County on its way to Washington D.C. John F. Kennedy spoke in front of the Butler County Courthouse during the 1960 United States presidential election. Hubert Humphrey also campaigned in Butler. In 2004, Vice President Dick Cheney spoke in Saxonburg to campaign for President George W. Bush in the 2004 United States presidential election.