Preterm birth risk differences per 1,000 births, with 95% confidence intervals, among non-Hispanic black women associated with increase from 10th to 90th percentiles of neighborhood non-Hispanic black density (17.8% to 88.9% black), Hispanic density (5.2% to 61.9% Hispanic), and Asian density (0.3% to 8.1% Asian). Risk differences were calculated for women aged 20-34 who were high school educated, had 2-5 previous live births, were nonsmokers, were on Medicaid, and resided in a more stable, poorer, and whiter neighborhood.