The section of modern NY 31 and NY 31A from NY 19 in Brockport to Clarendon was designated as New York State Route 3B in 1930, but was renumbered to New York State Route 3C  and the west end was cut back to the Monroe–Orleans county line before becoming New York State Route 31D . NY 31A was cut back to its current western terminus in 1949 and extended eastward to NY 19 and NY 31 in Brockport , replacing NY 31D.
In 1930, the section of modern NY 31 and NY 31A from NY 19 in Brockport to Clarendon was designated as New York State Route 3B. It later became New York State Route 3C with the west end cut back to the Monroe–Orleans county line before becoming New York State Route 31D. In 1949, NY 31A was shortened to its current western endpoint and extended eastward to NY 19 and NY 31 in Brockport, replacing NY 31D.