Coolspring Township municipal offices are located at 852 North Perry Highway, Mercer PA 16137.
In 1801 Coolspring was the name chosen to designate the southeast quarter of Mercer county. In 1802 this name was applied to what is now the east central portion of the county. In 1805 the township was restricted to about the area now comprised in Coolspring, Jackson, Fairview and Lake townships. In 1850 this area was divided into the four townships as they now stand, Coolspring being the southwest quarter of the former township of that name.
Benjamin Stokely was the first settler in Coolspring, in 1796. Other pioneers were Joseph and William Alexander, Aaron Hackney, Robert and Joseph McDonald, the Johnston family, Hugh McKean, William McMillan, the McEwens, and that notable pioneer preacher, Samuel Tait. Many of the associations dearest to the people revolve about the early Presbyterian churches of this township.
As Coolspring Township adjoins the borough of Mercer, the residents of the township from the early years have made this borough their principal trading point. William North, an Englishman, who settled in the northeast corner of the township about 1822, gave the name to the community which has been known as North's Mills. A post office was established there in May, 1858, and discontinued several years ago when rural delivery became general. Otter Creek became a post office in 1872, but has also been discontinued. Cool Spring station, a flag station on the railroad, marks this settlement.
Coolspring Township has come into prominence in recent years because of its oil wells. Otherwise it has for more than a century been rural community made up largely of Presbyterian farmers.