The designation proceeds northward as Portville-Eldred Road, paralleling the Allegheny River and ponds as a two-lane rural highway.

[5] In the town of Portville, NY 305 changes monikers to Portville-Obi Road, crossing into a two-lane rural highway.

Continuing along Dodge Creek, NY 305 parallels several residences before bending northward into the hamlet of Obi in the town of Clarksville.

Continuing northward, NY 305 enters the hamlet of West Clarksville, where the route becomes a two-lane residential street and an intersection with CR 40 (Jordan Hill Road).

After an intersection with CR 7, NY 305 parallels a railroad alignment into the town of New Hudson, where it enters the hamlet of Lyons Corners.

Northeast of Lyons Corners, the route enters the hamlet of Black Creek, where NY 305 intersects with CR 41 (Tibbetts Hill Road).

After, NY 305 enters the town of Belfast, paralleling several residences to the northeast and into the hamlet of Rockville, where the route turns eastward, crossing the former railroad right-of-way.

Paralleling the former railroad right-of-way, the route remains rural for several miles, intersecting with NY 19 (Transit Hill Road) in the town of Belfast.