- NY Route 104 runs along the corridor that was previously occupied by US Route 104. US Route 104 was decommissioned in 1972. US Route 104 ended at US Route 11 (then later Interstate 81) in Maple View, in which NY Route 126 then continued eastward to NY Route 13.
- Currently runs from the Canadian border at the Rainbow Bridge in Niagara Falls to NY Route 13 near Williamstown.
- Much of NY Route 104 between Rochester and Oswego was bypassed as a 2-lane expressway in the mid 1970s.
- Is a freeway between Eastman Ave in Rochester to the Monroe-Wayne County line, continues as an expressway further eastward before going to the aforementioned "Super-2" with at-grade intersections. Along this two lane portion is evidence of plans at one time of making it a four-lane expressway or freeway.
Please note: Mileposts are based on installed references as of February 2007. These mileposts conflict with the National MUTCD with New York State Supplement that goes into effect in September 2007, as the mileposts should show the distance from the western end of NY Route 104 at the Rainbow Bridge, instead of being based on the mileage from the beginning of this portion of freeway.