Created March 12, 1800 from part of Allegheny County and named for General Richard Butler, a military officer who was born in Ireland and came to America before 1760.. He served during the Revolutionary War as a Lieutenant Colonel in the Pennsylvania ranks and of Morgan's Rifle Corps in 1777. In l787, he was an agent for Indian affairs in Ohio, and on November 4, 1791, he was killed in a battle in that state while serving as a Major General with St. Clair in his expedition against the Indians.
Butler, the county seat, was first settled in l778, laid out in 1803 on land donated by Samuel and John Cunningham and Robert Graham. The town was incorporated as a borough on February 26, 1817, and chartered as a city on January 7,1918.
Butler County is bounded on the north by Venango County, on the east by Armstrong, on the south by Allegheny, on the west by Beaver and on the northwest by Mercer County.
Extensive tracts of land were laid out in 1785 by the State in lots of 200, 250, 300 and 500 acres which were given as gratuities to soldiers of the Revolution in the Pennsylvania Line, as Donation Land to re-imburse for the depreciation of currency issued as soldiers pay.
About the year 1800, Delman Basse Muller, a native of Germany purchased extensive depreciation tracts and in 1803 he sold a considerable portion to George Rapp and his associates. The borough of Harmony, in Jackson Township, had its inception in its settlement by the United Society of Germans familiarly known as Harmonists or Economites, who left their native home in search of religious liberty. George Rapp, their leader came to America in 1803 to find a location and prepare for the coming of the Society. He visited many localities and finally purchased 5000 acres from Dr. Delmar Basse Muller in Butler County on October 17, 1804. Three hundred of the Society arrived in Baltimore July 4, l804, a second colony arrived six weeks later at Philadelphia and were soon followed by a third. There were 135 families in the settlement at Harmony when the organization was perfected on February 15, 1805.
When it was determined to seek another home for the Society, the property consisted of 3000 acres of cleared land, 130 buildings, including a church, granary, tavern, two grist mills, houses and many other buildings. In 1809 the products were 6000 bushels of corn, 4000 bushels of wheat, 4500 bushels of rye, 5000 bushels of oats, 10,000 bushels of potatoes, 4000 bushels of flax and hemp and other products, more than the community could use.
The property was sold to Abraham Ziegler for $100,000 and in 1815 the Society moved to Posey County, Indiana and started the town of New Harmony. At the end of ten years they returned to Pennsylvania, founding the towns of Economy and Harmony on the east bank of the Ohio River, in Beaver Bounty, where George Rapp died August 7, 1847.