Simple, Straightforward, Wise, Insightful, Wry
The narrator is like a wise old guy who's seen it all. He doesn't embellish. He doesn't use flowery words or purple prose. He just puts it out there and describes the unfolding of history. But along the way, with the benefit of history and knowing how things worked out, our narrator offers up some opinions well.
He talks about immigrants, first saying: "They were filthy and illiterate. They stank of fish and garlic. They had running sores" (3.1), but then goes on to say: "But somehow piano lessons began to be heard. People stitched themselves to the flag. They sang. They told jokes" (3.3).
At first he's representing the opinions of the majority of New Yorkers at the time, and then bringing his own knowledge of the importance of immigrants to America to counterbalance those attitudes. It's something Doctorow does throughout, presenting people and places the way they're seen at the time and then later as people's perceptions change over time.