 The route followed its current alignment to west of Carmichaels, where it headed east by way of Carmichaels and New Salem to Uniontown.The alignment utilized a ferry across the Monongahela River.By the time of its inception, PA 21 existed as a paved road between Wind Ridge and PA 121 east of Waynesburg, in the Carmichaels area, and from south of Republic to Uniontown.