Map - Juniata County, Pennsylvania (Juniata County)

Juniata County is a county in the Commonwealth of Pennsylvania. As of the 2020 census, the population was 23,509. Its county seat is Mifflintown. The county was created on March 2, 1831, from part of Mifflin County and named for the Juniata River.

Mountains in Juniata County include Tuscarora Mountain and Shade Mountain. Agricultural land and forested land make up most of the county's area. Major rivers and creeks in the county include the Susquehanna River, the Juniata River, Tuscarora Creek, and West Branch Mahantango Creek. It borders seven other counties. The county lies over 16 different rock formations (which are from the Ordovician, Silurian, and Devonian) and 51 different soils.

Juniata County has a relatively low population density. The most population-dense parts of the county are the boroughs of Mifflintown and Mifflin. The main roads in Juniata County are Pennsylvania Route 235, Pennsylvania Route 35, Pennsylvania Route 104, U.S. Route 11/U.S. Route 15, U.S. Route 22/U.S. Route 322, Pennsylvania Route 74, Pennsylvania Route 850, and Pennsylvania Route 333.

The county has four boroughs and thirteen townships. It is served by two school districts, the Juniata County School District and Greenwood School District. There are five areas in Juniata County that are protected by the Central Pennsylvania Conservancy and 59 natural heritage sites in the county.

The first European settlers arrived in Juniata County in the 1750s. The county has historically been part of Mifflin County and before that, part of Cumberland County.

Juniata County was historically a part of Cumberland County and later Mifflin County. Juniata County was formed on March 2, 1831, from parts of Mifflin County. It is named after the Juniata River. The word "juniata" itself is a Seneca word that means either "people of the standing stone" or "blue waters". The first boroughs in the county to be settled were Mifflintown and Thompsontown, which were settled in 1790. Port Royal and Mifflin were settled in 1812 and 1848, respectively. The first of these boroughs to be incorporated was Mifflintown, on March 6, 1833, and the last was Thompsontown, on February 7, 1868. However, the first settlers (unauthorized squatters) arrived in the county and were removed from it considerably earlier, by 1750. One of the first warrants for land in the county was issued in 1755. Many of the earliest landowners in Delaware Township were speculators as opposed to settlers. There was an Indian raid in the county in 1755 and 1756, although Fort Bingham and Fort Peterson had been constructed. The Beale family was one of the earliest families to inhabit the county. More settlers arrived in the 1750s and 1760s and the first gristmill on the western side of the Juniata River was built in the county in 1767. A public road was built in the county between Tuscarora Creek and a location near Shade Mountain in 1768. John Hamilton constructed a sawmill and gristmill on Cocolamus Creek in Delaware Township in 1776. The first known physician in the county, Dr. Ezra Doty, settled in Mifflintown in 1791.

The first four townships in what would become Juniata County were formed on October 23, 1754. They were Lack Township, Aire Township, Fannett Township, and Tyrone Township. These early townships had no formal boundaries. By 1913, the original townships had been divided into a total of 13 townships.

The Pennsylvania Canal began serving Juniata County in 1826 and closed in 1900. The Pennsylvania Railroad reached the county in the late 1840s. The Tuscarora Valley Railroad was also in the county until it closed in 1934.

During Hurricane Agnes in 1972, a total of 6374 acres of Juniata County were flooded. 57 families were displaced during this flooding.

Juniata County was the last county in Pennsylvania to develop a modern comprehensive plan. It did, however, construct a comprehensive plan in 1974.