Borough municipal offices are located at 113 South Main Street, Mercersburg PA 17236; phone 717‑328‑3116.
Mercersburg Chamber of Commerce is located at 19 North Main Street, Mercersburg PA 17236.
First settled about 1729, laid out around 1780, the borough was incorporated in 1831.
Believed to have been settled during the second and third quarters of the 18th century, Mercersburg was laid out as a town in 1786. It was named for General Hugh Mercer a Revolutionary War officer and doctor who lived near the town. The village began as a trading center, mill and tannery site owned by James Black and located on a major road to the west. It was established by William Smith who acquired the site in 1759. His house, it is believed, still stands, a stone and frame structure in the north end of town, outside the district. Smith's tannery was located nearby on Campbell's Run which passes through the north part of town. Eventually the wagon road, now Pennsylvania Route 16, was superseded by other turnpikes to the north and south leading from Philadelphia and Baltimore respectively, westward, taking the town out of the main stream of commerce and travel. In the 19th century, Mercersburg became an educational center with the establishment in 1835 of a Seminary of the German Reformed Church. The Theological Seminary remained in Mercersburg until 1871. Marshall College was also located here, later merging with Franklin College in Lancaster, Pennsylvania in 1853. In 1893 Mercersburg Academy, a preparatory school for boys was founded.