Herndon, formerly Trevorton Junction, is a borough in Northumberland County, Pennsylvania, United States. Herndon was first founded by Robert A. Parrish in 1840. The town was later named for Naval commander William Lewis Herndon, who died in 1857 while trying to rescue passengers from his sinking ship. The population was 324 at the 2010 census.
Herndon is located at 40°42′15″N 76°50′36″W / 40.70417°N 76.84333°W / 40.70417; -76.84333 (40.704241, -76.843212).
According to the United States Census Bureau, the borough has a total area of 1.8 square miles (4.6 km²), of which, 0.8 square miles (2.1 km²) of it is land and 1.0 square miles (2.5 km²) of it (55.06%) is water.