Over its routing, NY 31 spans 10 counties and indirectly connects three major urban areas in Upstate New York: Buffalo–Niagara Falls, Rochester, and Syracuse.

Much of NY 31 west of Jordan was originally designated as part of a legislative route from the late 1900s to the early 1920s.

In return, the state acquired a pair of county roads that followed a routing parallel to that of the transferred section of NY 234.

[6] The portion in Newark, meanwhile, extends from Mason Street (one block west of NY 88) to the eastern village line.

The busiest of these, from Interstate 590 (I-590) to NY 65 in the eastern suburb of Brighton, carries in excess of 40,000 vehicles per day on average.

Two other segments—between South and Woodbury Avenues in downtown Rochester and from NY 65 to French Road in Brighton and Pittsford—have traffic volumes in excess of 30,000 vehicles.

NY 31 continues northeastward into the town of Niagara, following Witmer Road to an interchange with I-190 at exit 24.

The route quickly leaves Holley soon after, crossing into Monroe County just over a mile (about 1.6 km) from the village line.

It heads onward toward a pair of overpasses, one carrying I-490 and another holding the CSX Transportation-owned Rochester Subdivision.

Just east of Exchange Boulevard, the northern terminus of NY 383, the route crosses the Genesee River on the Broad Street Aqueduct.

[11] Over this stretch, NY 31 maintains a constant southeasterly progression as it passes through southeastern Rochester and the town of Brighton.

Just inside the village limits, NY 31 crosses the Erie Canal once more and intersects the West Shore Subdivision at-grade.

Outside of the village, NY 31 parallels I-490 for a short distance across slightly open areas before connecting to the freeway near the Perinton town line at exit 26.

[12] East of the mall, the route passes through increasingly rural areas, with the exception of the hamlet of Egypt midway between NY 250 and the Wayne County line.

The highway continues on, exiting the village and proceeding eastward through the town of Macedon, bordered by the Erie Canal to the north and Ganargua Creek to the south.

Outside of Clyde, the Erie Canal veers off to the southeast while NY 31 continues east alongside the Rochester Subdivision to the hamlet of Savannah, the final centralized community within Wayne County.

The alignment remains fairly straight to the outskirts of Baldwinsville, where NY 31 turns to the right onto Downer Street to avoid the Seneca River to the immediate north.

NY 31 continues eastward, crossing the creek and entering Madison County and the remaining portion of Bridgeport.

[8] East of Bridgeport, NY 31 moves closer to Oneida Lake, eventually coming to within 200 yards (180 m) of the lakeshore at points.

The Turning Stone Resort & Casino, located 2 miles (3 km) south of the intersection, is accessible via NY 365.

The route continues eastward into the center of the community, where it ends at a large traffic circle with NY 26.

Outside of Baldwinsville, NY 31 remained on its current routing to Cicero, where it followed a more northerly alignment along Lakeshore Road.

[24][25] US 104, meanwhile, was assigned c. 1935, following Ridge Road from Niagara Falls east to Maple View in Oswego County.

NY 31 was altered c. 1938 to follow its modern alignment through Cicero, bypassing Lakeshore Road to the south.

[38][39] The section of the route between Middleport and Medina was shifted southward on January 1, 1949, to follow what had been NY 31A between the two villages.

[40] The portion of NY 31 northeast of Jordan was straightened at some point in the late 1970s or early 1980s to bypass the hamlet of Jacks Reef to the south and east.

[42] The Redman Road portion of NY 31, meanwhile, was initially maintained by Monroe County as part of CR 236.

Under the terms of the act, it took effect 90 days after it was signed into law; thus, the maintenance swap officially took place on November 26, 2007.

[44] The portion of NY 31 in downtown Rochester between Brown Street and South Avenue runs along the old path of the Erie Canal through the city.

[50] The entire project, which also calls for landscape improvements to the area surrounding West Broad Street, was tentatively scheduled to be finished in February 2012.