It is 26.49 miles (42.63 km) in length and runs from CR 353 in Rensselaerville to Interstate 90 (I-90) exit 4 in Albany.

NY 85 begins at the north end of the County Route 353 (CR 353; Delaware Turnpike) bridge over the Ten Mile Creek in the hamlet of Rensselaerville.

Crossing into the town of Berne, NY 85 meets a junction with CR 11 (Cass Hill Road) west of the hamlet of Reidsville.

The route then bends northward at this junction, bypassing the hamlet and soon reaching the northern terminus of CR 11 (North Road) nearby.

Still a two-lane road through New Scotland, NY 85 passes multiple residences before making a large curve to the north.

[3] The route bends northeast and enters the area of New Salem Hill, where it intersects with the eastern terminus of NY 157 (Thacher Park Road).

Through New Salem, NY 85 is a two-lane residential street, soon leaving the hamlet after Mountain View Estates Road.

The route runs northeast through the hamlet, becoming a two-lane residential/commercial street and intersects with CR 308 (New Scotland South Road).

Through Bethlehem, NY 85 reaches the hamlet of Slingerlands, becoming a two-lane residential street and crossing the eastern terminus of CR 306 (Font Grove Road).

[3] Almost immediately after US 20, NY 85 continues past another interchange, serving Washington Avenue and the W. Averell Harriman State Office Building Campus.

[3] The path of modern NY 85 west of Slingerlands roughly follows that of the Albany, Rensselaerville, and Schoharie Plank Road, a plank road established to connect the city of Albany with the town of Schoharie by way of passing through Rensselaerville.

The Albany, Schoharie, and Rensselaerville Plank Road Company was organized on October 10, 1849, with Lansing Pruyn as president.

The section from New Salem east to the hamlet of New Scotland subsequently had its planks removed and the portion from Bernville to Gallupville was also abandoned.

The first section of the bypass from Washington Avenue to Buckingham Drive (the Krumkill Road exit) was completed by 1964.