One of the most iconic symbols of Appalachian culture— the banjo— was brought to the region by African-American slaves in the 18th century. Black banjo players were performing in Appalachia as early as 1798, when their presence was documented in Knoxville, Tennessee. African-American blues, which spread through the region in the early 20th century, brought harmonic (such as the third and seventh blue notes, and sliding tones) and verbal dexterity to Appalachian music, and many early Appalachian musicians, such as Dock Boggs and Hobart Smith, recalled being greatly influenced by watching black musicians perform.