Plank roads were a feature of American transportation in the mid-19th century, the first being constructed in Michigan (1837) and New York (1844). When they were properly maintained they provided a smooth surface, and should not be confused with log ‘corduroy’ roads that were often quite dangerous. Construction consisted of laying planks of pine or oak, eight to sixteen feet long and three to four inches thick, across ‘sleepers’ or ‘stringers’ that had been placed parallel. Personal footnote: US 220 in Altoona where I grew up was known as "Plank Road". I don't think anyone there knew this song. This is a classic from Uncle Dave Macon who recorded it with Sam McGee. Macon sang and played banjo, sometimes with a group called the Fruitjar Drinkers. Uncle Dave's version is in the Folkways Anthology of American Folk Music. The verses are borrowed from many sources. It was also recorded by the New Lost City Ramblers.