Lewistown is a borough in and the county seat of Mifflin County, Pennsylvania, United States. It lies along the Juniata River, 61 miles (98 km) northwest of Harrisburg. The number of people living in the borough in 1900 was 4,451; in 1910, 8,166; and in 1940, 13,017. The population was 8,998 at the 2000 census, and estimated at 8,466 in 2009 according to the US Census Bureau. It is the principal borough of the Lewistown Micropolitan Statistical Area. Of the four communities in the United States named "Lewistown", this borough is the largest.
The borough was incorporated in 1795 and was named for William "Bill" Lewis, a Quaker and a member of the legislature, who was responsible for the designation of the borough, which was then known as the Village of Ohesson, as the county seat of Mifflin County.
During the late 19th century Mifflin County became the crossroads of the Commonwealth. Located near the geographic center of the state, the area became a hub for traffic moving in every direction.