By 1926, NY 31 was assigned across western and central New York, utilizing Monroe Avenue from downtown Rochester to Pittsford. Although NY 96's modern routing via East Avenue was state-maintained and formerly part of legislative Route 20 from current NY 31F westward, NY 15 initially remained on Monroe Avenue, creating an overlap between NY 15 and NY 31. It was realigned at some point between 1927 and 1932 to follow East Avenue to Rochester instead. In southern Seneca County, NY 15 initially passed through Lodi on its way from Interlaken to Ovid. It was realigned in the late 1920s to bypass Lodi to the northeast on the former alignment of legislative Route 36.