Tupper Lake was, once upon a time, Tupper Lake Junction, where the Mohawk & Malone (later the New York Central's Adirondack Division) met the obscure New York & Ottawa (earlier the Northern Adirondack Railroad and Northern New York Railroad, later the equally obscure New York Central Ottawa Division) at the NY&O's southern terminus.

The Northern Adirondack Railroad was chartered February 9th, 1883 to extend from the Ogdensburg and Lake Champlain Railroad (later the west end of the Rutland) at Moira, NY southeast to St. Regis Falls, NY. It was extended further south to Santa Clara, NY in 1885 but those rails remained inactive after completion.
The Northern Adirondack Extension Railroad was chartered on February 17, 1886, to take over the existing but inactive rails between St. Regis Falls and Santa Clara, as well as to continue to extend the Northern Adirondack Railroad southeast to Tupper Lake. Tupper Lake was home to what was the largest saw mill in the US at the time, and Seward Webb's Mohawk & Malone was still six years from even beginning construction north from Herkimer through Tupper Lake and roads through the Adirondacks were practically nonexistent, so this was prime pickings for a railroad.
Right across the border at Cornwall, Ontario, politicians were planning the Ontario Pacific Railway. And that's basically all they did from 1882 until 1897. A number of plans were discussed of a railroad headed west from Cornwall, with the final ambitious plan being that the proposal would follow a route west from Cornwall to Embrun to Richmond to Perth to Lake St. Peter to French River to Sault Ste. Marie, but no construction ever began.
The Northern Adirondack Railroad went into receivership on January 25, 1894. On May 25, 1895, the railroad was sold to a business syndicate and two days later was renamed the Northern New York Railroad. The driving force behind the Northern New York Railroad, Charles Hibbard, planned to extend further southeast from Tupper Lake to Axton Landing. From that point, the D&H had planned to extend its Adirondack Branch, which terminated at North Creek, to Axton Landing under the Northern Adirondack Extension Railroad charter. Hibbard's trains were to have trackage rights to Saratoga Springs, and then on to New York City. Hibbard also planned to build northward into Canada. At first, the plan was to take over the Saratoga & St. Lawrence Railroad and then head to St. Regis in Quebec, and then from there, Hibbard's line would build to Ottawa. From June 11 to July 30, 1896, the Northern New York Railroad operated the Saratoga & St. Lawrence Railroad, but for unknown reasons Hibbard was not pleased with it, and instead, he planned to build northward from Moira himself, and a new company was created to do so. After meeting Dr. Darby Bergin from the Ontario Pacific Railway, Hibbard formed a partnership with him and these two railroaders planned to connect Ottawa to the Adirondack line. With that merger and the D&H extension to Axton Landing and trackage rights, the Northern New York would connect Ottawa to New York City.
Bergin renamed the Ontario Pacific Railway to the Ottawa & New York Railway and began construction from Ottawa to Cornwall, as well as to construct a bridge crossing over the St. Lawrence River at Cornwall. Construction began on August 23rd, 1897 and was quickly completed, opening on July 29, 1898. Meanwhile, Hibbard formed the New York & Ottawa Railroad to build from the northwest terminus of the Northern New York Railroad at Moira up to the St. Lawrence River to connect to the Ottawa & New York. On October 28th, 1897 the Northern New York was merged into the New York and Ottawa. The NY&O acquired the O&NY's stock on June 13th, 1898 and on September 28th of that year, the line in New York was completed, running to the St. Lawrence River at Roosesveltown, NY. The extension south from Tupper Lake to Axton Landing, as well as the D&H's northward extension from North Creek to Axton Landing never came to pass, although the NY&O began construction south of Tupper Lake Junction (where the NY&O met the NYC Adirondack Division) was started. Environmental preservationists were not fond of the idea of a second railroad being built through the forest, and the NYC, who brooked no intrusions in their territory, likely applied influence to bar construction as well. Thus, Hibbard's hopes of connecting to New York City never occurred under his ownership. The entire route from Ottawa to Tupper Lake was finally operating on October 1, 1900, after the company entered receivership on April 25, 1900.
The New York & Ottawa Railroad company was sold to New York Central interests on December 22, 1904 and became the New York & Ottawa Railway on January 19, 1905. This was followed by the company being leased to the New York Central on February 1 and renamed to the Ottawa Division. This actually ended up accomplishing Hibbard's goals, albeit under a different routing, since one could then take an NY&O train from Ottawa to Tupper Lake, hop an Adirondack Division train from Tupper Lake to Herkimer, and then transfer onto a mainline train at Herkimer to go to New York City.
The Ottawa Division seems to have never been particularly busy or profitable, and I have to imagine that NYC acquired less out of thinking it would be a huge moneymaker and more out of their imperious attitude of squashing any possible competitor in their region. The line was abandoned from Tupper Lake Junction to Helena on May 6, 1937, and then from Rooseveltown (Akwesane) to Ottawa on March 22, 1957, leaving just 5 miles between Helena and Rooseveltown that is still in service to this day under CSX. The bridges over the St. Lawrence River at Cornwall were removed to make room for the St. Lawrence Seaway, with the south span removed in 1958 and the north span removed in 1965. Meanwhile, Canadian National purchased the Canadian portion of the route in April 1957, specifically to yank up the rails to use to build a new hump yard in Montreal.
New York & Ottawa 4-4-0 #3 at Tupper Lake sometime between 1897 and 1905.