Symbolism, Imagery, Allegory
Doctorow named his novel Ragtime for a very valid reason: it represents the last time America moved at such a slow, measured pace. As Scott Joplin, who composed the Maple Leaf Rag and other famous ragtime pieces, says in the epigraph of the book: "Do not play this piece fast. It is never right to play Ragtime fast..."
This period of time is kind of when America caught its breath, just before launching into the two World Wars, the craziness of cars and technology, and finally TV, computers and the smartphones we're all walking around with today.
Even the way Doctorow tells his tale matches the pace and style of Ragtime music... the book's sentences are short and steady, like the "small clear chords" (21.8) of "Wall Street Rag."
It's also worth noting that ragtime music is totally a precursor to jazz. The Jazz Age signaled the collective loss of American innocence. But the Ragtime Age was still clinging to the last scraps of innocence left over from the 19th century… even as it paved the way for the faster, louder, more hedonistic future.