Made famous as line between free and slave states before War Between the States. The survey establishing Maryland-Pennsylvania boundary began, 1763; halted by Indian wars, 1767; continued to southwest corner, 1782; marked, 1784.
Site of Baldwin blockhouse, 1770-1775. Brice and Nathan Worley settled here in 1766. Nathan was killed by Indians in 1777. Laid out as a town in 1829 and lots sold through a lottery. Town is named for David Black, early settler.