Danville is a borough in Montour County, Pennsylvania, USA, of which it is the county seat, on the North Branch of the Susquehanna River. Danville was home to 8,042 people in 1900, 7,517 people in 1910, and 7,122 people in 1940. The population was 4,699 at the 2010 census.
Iroquois land until a 1768 treaty, Chester County native and American Revolutionary War figure William Montgomery purchased a plot of land in 1774 and established a trading post called Montgomery's Landing. In 1792 he constructed a house there, which is now a small museum inside the town. In the same year his son Daniel plotted the area between Mill Street and Church Street, the historic core of the town which now bears his name.
Danville was part of Northumberland County, Pennsylvania, when it was founded. In 1813, Columbia County, Pennsylvania was formed from part of Northumberland Co. Danville became the county seat of Columbia Co. until 1845, when an election moved the seat to Bloomsburg, Pennsylvania. In 1850, Montour County was formed from part of Columbia. Danville then became the county seat of Montour.
Danville became a transportation center in the 19th century, served by several railroads and the North Branch of the Susquehanna River. Coal and iron mines in the surrounding hills and mountains fueled the local economy, and by mid-century Danville was an important iron mill town. Many of the rails of the nation's expanding railroad system were made in Danville. A local marker claims that the first T-rail rolled in the United States was rolled in Danville, on October 8, 1845 at the Montour Iron Company, though this is claimed for Mount Savage, Maryland, as well.
Montour and several other enormous iron mills dominated the town for most of the 19th century and the iron industry was the chief employer in the region. The iron mills fell into decline, however, as steel replaced iron in the 20th century. The city celebrates this era with an annual Iron Heritage Festival in July, and the main street is still named "Mill Street".
In 1869 the Danville State Hospital was built as a state institution for the treatment and care of the insane.
Abigail Geisinger, widow of iron magnate George Geisinger, used his fortune to build a hospital and clinic intended to be a regional medical center modeled after the Mayo Clinic. The Geisinger Hospital was completed in 1915, and has grown over the years. Today, the Geisinger Medical Center is the most important tertiary referral center in northern Pennsylvania. Geisinger and its affiliated institutions are also one of the largest employers in the region.
The Thomas Beaver Free Library and Danville YMCA, Danville Historic District, Danville West Market Street Historic District, and Gen. William Montgomery House are listed on the National Register of Historic Places.