This section of NY 33 is one of several freeways leading out of downtown and serves as a main route to the Buffalo Niagara International Airport.

On the Rochester end, NY 33 primarily serves as a paralleling local route to Interstate 490 (I-490), of less importance to the area's traffic patterns.

It was extended on both ends—to Buffalo in the west and Marion in the east—as part of the 1930 renumbering of state highways in New York; however, the eastern extension was eliminated in 1949.

Smaller realignments in the years since have moved NY 33's western terminus from the heart of downtown Buffalo to the northern fringe of the city's center.

[4][5][6] The Kensington Expressway was constructed in 1958, in the place of the Humboldt Parkway, and radically changed the nature of majority-Black neighborhoods on the east-side of Buffalo.

Both intersect with NY 5 (Ellicott Street) in Buffalo, from where they serve as a one-way couplet for three blocks before they merge to become the Kensington Expressway, a freeway.

Past Harlem Road, the expressway makes a slight curve to the south as it prepares to meet a toll-free section of the New York State Thruway (I-90) at a cloverleaf interchange.

After another 0.5 miles (0.8 km), NY 33 curves south under Genesee Street before joining it at a traffic light in front of the Buffalo Niagara International Airport.

[10] Now returning to its pre-Kensington route, NY 33 follows a six-lane, divided Genesee Street past the airport on one side and numerous associated businesses such as hotels and fast food restaurants on the other.

After this junction, the highway becomes a two-lane route once again through the small hamlet of Bowmansville, where it crosses Ellicott Creek near some rapids.

Much of this section of Lancaster has remained rural in character;[10] however, that began to change in the mid-1990s when Tops Friendly Markets, the regional supermarket chain headquartered in nearby Williamsville, chose a site near the Gunnville Road intersection for a major distribution center.

The route continues on a northeastward course into the town of Stafford, where it crosses over the CSX Transportation-owned Rochester Subdivision railroad line and the Thruway by way of overpasses less than 1 mile (1.6 km) apart.

[10] It remains close to the Interstate Highway for about 4 miles (6 km), intersecting NY 237 less than a mile (1.6 km) north of the overpass taking that highway over the Thruway, but leaves it behind for good shortly thereafter as it turns even more to the north, taking it into the town of Bergen and the small village of the same name in the county's northeast corner.

It connects to Mount Read Boulevard by way of a signalized traffic circle before abruptly turning southward to pass under the tracks and meet up with West Avenue.

At the time, state maintenance of this segment began at the Buffalo city line and ended at current NY 77 in Corfu.

[23][24] The remainder of the highway was completed c. 1965, at which time NY 33 was realigned to follow the new expressway from Michigan Avenue to the airport.

[30][31] In January 2022, Governor of New York Kathy Hochul announced that $1 billion was set aside for the construction of a 0.75-mile (1.21 km) long cover over the Kensington Expressway, reconnecting parts of Humboldt Parkway disconnected by the highway.

[33] Update: As of October 31, 2024, a New York Supreme Court decision has placed an extended Temporary Restraining Order on the NY 33 Kensington Expressway Project, after East Side Parkways Coalition, and over 60 Humboldt Parkway Neighborhood plaintiffs, and several other petitioners, including Citizens For Regional Transit, WNY Youth Climate Council, and the New York Civil Liberties Union, filed for an Injunction.

The goal of the court action, is to require New York State Department of Transportation, the co-lead agency of the project, to furnish an Environmental Impact Statement or EIS, fully exploring alternate approaches to the expressway project, and addressing widespread complaints that NY Route 33 Kensington Expressway is responsible for inflicting pervasive air and noise pollution that has adversely impacted the health of countless Kensington Expressway Corridor neighborhood residents.