It served as a connector between NY 31, its parent route, in the Cayuga County village of Weedsport and NY 5 in the Onondaga County town of Elbridge.

NY 31B was assigned c. 1933, replacing New York State Route 293, a route assigned as part of the 1930 renumbering of state highways in New York.

The highway went eastward, intersecting with NY 34 less than 0.1 miles (0.2 km) later.

Much of Weedsport was urbanized, with the highway passing residential homes and businesses as it progressed eastward through the village.

[4] Ownership and maintenance of NY 31B's former routing was gradually transferred to the counties it went through, namely Cayuga and Onondaga.