It begins at the Ohio state line in rural Erie County, Pennsylvania, and travels through several cities and villages (including the cities of Buffalo, Niagara Falls, Rochester, Oswego, and Ogdensburg) before ending at the Seaway International Bridge northeast of the village of Massena in St. Lawrence County, New York.

There, the Seaway Trail traverses the counties of Chautauqua, Erie, Niagara, Orleans, Monroe, Wayne, Cayuga, Oswego, Jefferson, and St.

[7] Points of interest along the Chautauqua County piece of the trail include the Barcelona Lighthouse in Westfield, Lake Erie State Park, and the city of Dunkirk.

In Erie County, aside from the many attractions in the city of Buffalo, nearby destinations include Highmark Stadium in Orchard Park and a series of three museums in East Aurora.

River Road becomes Buffalo Avenue when it enters the city of Niagara Falls, and soon Route 265 splits off to the north.

Route 384 continues westward, where the Seaway Trail picks up the Robert Moses State Parkway at its eastern terminus at the northern Grand Island bridge, which carries Interstate 190 (I-190).

[7] The Robert Moses Parkway follows extremely close to the river to Quay Street; continuing west would take drivers directly into Niagara Falls State Park, but the Seaway Trail instead uses Quay Street to access Rainbow Boulevard, which was once part of NY 384.

North of Youngstown, Route 18F comes very close to the mouth of the Niagara River and swings eastward, now following the Lake Ontario shoreline.

[7] Aside from the Falls themselves, and the twin cities of Niagara Falls on either side of the border, nearby attractions include Artpark in Lewiston, the Erie Canal Junction at Tonawanda Creek, the Herschell Carrousel Factory Museum in North Tonawanda, Fort Niagara in Youngstown, and Golden Hill State Park in Somerset.

[7][8] The Seaway Trail follows Route 18 eastward about halfway through Orleans County, where it switches onto the Lake Ontario State Parkway at its western terminus.

The Parkway continues east, coming very close to the Lake Ontario shore at times, until crossing the border into Monroe County.

[7][8] The Seaway Trail continues along the Lake Ontario State Parkway to its eastern terminus just inside the city of Rochester.

Now on Pattonwood Drive, the trail almost immediately exits this narrow strip of the city and enters the town of Irondequoit.

NY 404 begins a short distance along Empire Boulevard, and the trail follows them east and north-northeast along the shore of the bay.

The route avoids the longer trip (11.8 miles or 19.0 kilometres) around the bay to the south and takes in additional scenic landmarks such as Seabreeze Amusement Park and the jetties at the outlet.

[7] In either case, Lake Road carries the Seaway Trail eastward along the northern edge of the town of Webster to the county line.

Route 104A turns east toward the hamlet of Sterling, then north again before again moving northeast, paralleling the Lake Ontario shore at a distance of about two miles (3.5 km).

The Seaway Trail follows Route 3 northeast, then north, crossing the Salmon River at Port Ontario.

To the direct east, Cayuga County is relatively thin near Lake Ontario, so the Seaway Trail doesn't take long to pass through it.

Fair Haven Beach State Park is nearby, and in July and August, travelers can visit the Sterling Renaissance Festival.

Route 12 continues to carry the Seaway Trail northeast to the county line, passing through Alexandria Bay.

[7] Route 37 continues northeast and starts to turn slightly eastward as it approaches the top of New York State, passing through the village of Waddington.

This is the point at which New York's northern border straightens out and proceeds due east (along the 45th parallel north) rather than following the St. Lawrence River, which cuts through Quebec.

[7] Attractions along this northeasternmost segment of the Seaway Trail include Singer Castle, the Frederic Remington Art Museum in Ogdensburg, the Eisenhower Locks on the river near Massena, and a few more historic lighthouses.

[2] The route was recognized as one of the "Top 50 Most Comfortable Touring Drives" in the nation by the Goodyear Tire and Rubber Company in October 2010.

[17] Since its inception in 1978, the trailblazers along the byway had been white-on-green signs with a pair of footprints adjacent to the words "Seaway Trail".