Beaver County, Pennsylvania: History
Beaver County was created on March 12, 1800, from parts of Allegheny and Washington counties. It took its name from the Beaver River.
The original townships at the date of the erection of Beaver County in 1800 were North Beaver, in what would eventually become Lawrence County, east and west of the Big Beaver Creek; South Beaver, west of the Big Beaver; Sewickley, east of the Big Beaver—all north of the Ohio River; Hanover, in the southeastern corner of the county; and lastly, First Moon, and Second Moon, south of the Ohio.