Through the mid-1800s, Watertown became a valuable and crowded railroad with The Rome, Watertown & Ogdensburg, the Carthage Watertown & Sackets Harbor (later the Utica & Black River),, and the Potsdam & Watertown railroads building track into and in the city. The first railroad station, "Watertown Junction", was at the foot of Stone Street where the RW&O trains stopped before continuing through Brownville, Limerick and Chaumont to Cape Vincent and back. Moving people and cargo to and from Lake Ontario's busy shipping lanes and connecting to Canada and Europe was one of the major aims of the railroads.
All three railroads eventually became the RW&O, later to be folded into Cornelius Vanderbilt's New York Central. In 1870, railroad roundhouses were on Coffeen Street where Verizon is now (RW&O) and behind what is now Morrison's Furniture (CW&SH).
The New York Central Railroad began building a massive new yard in 1918, which cut off existing streets (West Mullin, Pine, Willow, Smith, Dorsey, Duffy, Casey and Coleman), and made the area across from Cross and West Mullin streets up to 26 tracks wide.
Because of the arrival of diesel engines which required much less maintenance and trip preparation than coal-burning steam trains, the "Pine Street Yard" was only used until the 1940s and largely demolished in the 1950s, replaced by the present yard on outer Massey St.
The piece of the Pine St. Yard was a giant 30-bay roundhouse to repair and maintain engine/tender combinations. 767 feet from tip to tip, the facility had concrete repair platforms with bays underneath the engine tracks to access the bottoms. A system of drains let boiler water drain away quickly.
While the roundhouse was "torn down" in 1953, much of it was never hauled away and is still there. The concrete repair aprons are still there AND the 100' diameter pit that used to held the massive turntable to swing engines and cars to different tracks is also still there.
No signs remain of the giant coal trestle west of the roundhouse where railroad cars full of coal were pushed up a long ramp to one of two tracks in the enclosed "house" on top of the huge timber structure. Doors on the bottom of the coal cars opened, dumping coal into bins. Locomotives and their tenders pulled along side of the trestle and chutes would fill the tenders with coal in about a minute, then they'd move down the line to fill up with water and sand (for traction), all in one stop.
Some area coal dealers would also get coal there by the wagon or truckload. An old truck scale and its scalehouse still stands at the end of Duffy Street.
Next to the roundhouse was a power house that made all the steam, heat, cooling and compressed air for the yard. It had its own coal trestle. That property and much of the rest of the yard is covered by the Public Safety Building, but there are many other remnants of the yard--if you know where to look.
Carpenter, welding, blacksmith, electrical, plumbing, upholstery and other shops and offices filled other parts of the yard. A track that connected Watertown with Sackets Harbor ran along the north edge of the yard; the old railbed can be easily traced by looking at satellite pictures of the area from Bing or Google; you can go from behind K-Mart all the way to the big curve into Sackets.