Stephen, I don't think the streets were initially covered with cobblestones but were in fact just dirt roads to start with.
I found some info in Malone's biography of Jefferson -- the volume on TJ's first term, p.47. The roads at the outset were were supposed to be gravel. More info on later improvements is on p. 367. I don't see anything about when roads were paved. Must have occurred much later but I'd suggest looking at biographies and papers of persons in office in later periods.
I found some info in Malone's biography of Jefferson -- the volume on TJ's first term, p.47. The roads at the outset were were supposed to be gravel. More info on later improvements is on p. 367. I don't see anything about when roads were paved. Must have occurred much later but I'd suggest looking at biographies and papers of persons in office in later periods.