All of the route within Niagara County, excluding the state-maintained overlap with NY 271 in Middleport, is county-maintained as the unsigned County Route 143 (CR 143). In Medina, NY 31E is entirely maintained by the village, though between the village line and Prospect Avenue (former NY 63), it was NYSDOT-maintained for  to its terminus at NY 31 until 2010.
All of the route within Niagara County, excluding the state-maintained overlap with NY 271 in Middleport, is county-maintained as the unsigned County Route 143 (CR 143). In Medina, NY 31E is entirely maintained by the village, though between the village line and Prospect Avenue (former NY 63), it was state-maintained until 2010.