Although the entirety of modern NY 408 was state-maintained by 1926, only one section of the route—the portion designated as part of legislative Route 15—was assigned a posted route number by that time. In the mid-1920s, this piece was designated as part of NY 36, which initially continued north to Geneseo on modern NY 63.
By 1926, most of modern NY 408 had been state-maintained, but only a specific section—designated as legislative Route 15—had received a posted route number. In the mid-1920s, this segment was reclassified under NY 36, which initially extended north to Geneseo on modern NY 63.