Railroads probably a big contributor to the timing of development, which probably also led to road improvements since you'd need to be able to get around once you got off the train. Recently read my great grandfather's diaries, who wrote of hopping on a train from CT to Brattleboro, then up to Ludlow to sell books and magazines door to door for a Summer in the 1890s. He bought a bicycle in Brattleboro and used that to get around locally so roads were probably pretty good by then. He wrote about riding his bike from Ludlow up to Proctorsville. Must have been an absolutely gorgeous ride back then (still is today), though also probably a bit challenging with books in tow!