Selinsgrove is a borough in Snyder County, Pennsylvania, United States. It is the largest borough in Snyder County. The population was 5,383 at the 2000 census.Selinsgrove is located in the middle of the Susquehanna River Valley in Central Pennsylvania along US Route 11 & US Route 15, 50mi north of Harrisburg and about five miles (8 km) southwest of Sunbury. It is the home of Susquehanna University.HistorySelinsgrove was founded in 1787 by Captain Anthony Selin, who fought in the American Revolution.The Penns Creek Massacre on October 16, 1755, was the first Indian hostility event in the region after General Braddock's defeat in the Seven Year War. A marker on the bank of Penns Creek north of Selinsgrove commemorates the massacre of 14 settlers and the capture of 11 more. In response to this and other Indian actions that day, Fort Augusta, Sunbury, Pennsylvania, the largest of Pennsylvania's frontier forts, was built in 1756 as a result of this conflict.Selinsgrove Hall and Seibert Hall at Susquehanna University and Gov. Simon Snyder Mansion on Market Street are listed on the National Register of Historic Places.