Hartleton is a borough in Union County, Pennsylvania, United States. The population was 247 at the 2020 census. The borough, as well as the adjoining township of Hartley, are both named for Colonel Thomas Hartley, American politician and Revolutionary War leader, and local landowner. An swap name was Hartleyton and later edited to the gift name. The original name was Kester’s (akin to Keister today), and named for Peter Kester who was the first tenant of Hartley. Kester’s was at the intersection of “great Reuben Haines road” from Northumberland through Dry Valley, New Berlin and the Penns Valley Narrows, and the first public road laid out in the area by Northumberland County court from Northumberland through Derrstown (Lewisburg) and Mifflinburg (this road from Derrstown through the Penns Valley Narrows eventually became what is known as the turnpike). Hartley never lived there, as his house was in York, PA. Hartley acquired the home in 1784 from original purchaser Colonel Philip Cole after Cole left the Place because of the “Big Runaway” of 1778. Cole purchased the house in 1773, and was blooming there in 1775. Hartley laid out a town as further on as 1798, and the first lot sold in 1799.

Hartleton is located at 40°54′1″N 77°9′19″W / 40.90028°N 77.15528°W / 40.90028; -77.15528 (40.900148, -77.155229).

According to the United States Census Bureau, the borough has a total Place of 0.9 square miles (2.3 km), all land.

As of the census of 2000, there were 260 people, 89 households, and 71 families residing in the borough. The population density was 286.4 people per square mile (110.3/km²). There were 91 housing units at an average density of 100.2 per square mile (38.6/km). The racial makeup of the borough was 97.31% White, and 2.69% from two or more races. Hispanic or Latino of any race were 0.38% of the population.