It heads to the northwest as Boston State Road, passing by suburban homes as it approaches the Southern Expressway (US 219).

West of the exit, NY 391's surroundings become more rural as it enters the town of Hamburg, where it passes by open fields and a handful of houses.

[3] The route follows Eighteen Mile Creek northwest and west toward the village of Hamburg, where the amount of development along the highway increases significantly.

At McKinley Parkway (County Route 204), NY 391 becomes East Main Street and begins to pass through the outskirts of the village.

The route continues into the village center, passing by commercial and residential buildings on its way to a roundabout at Buffalo Street, where it meets US 62.

[10] In the early 1970s, construction began on the Southern Expressway, a limited-access highway connecting Buffalo to Springville.

[15][16] The remainder of US 219's former routing south to Springville was transferred to Erie County upon the completion of the Springville–Buffalo segment of the Southern Expressway.