Limestone, lying under Whitehorse and exposed on Canyon Mountain, was deposited here over 200 million years ago and, over time, was covered by 10 kilometres of sediment. About 110 million years ago, magma rose up from below the earth's crust carrying dissolved minerals that reacted with the limestone to form deposits of copper ore. Erosion of the overlying rocks made the deposits accessible to the nearly 20 mines that operated in the Whitehorse Copper Belt during the early 1900s.
Prospectors heading for the Klondike Goldfields discovered the copper in 1897. Jack McIntyre staked the first claim, Copper King, in July 1898 and a few other claims were also staked that summer. McIntyre and his partner William Grainger sent the first ore to the smelter in 1900 and miners at Pueblo claim sent out an ore sample from what would prove to be the richest and most productive of the early mines.
Pueblo used the spur line sporadically between 1910 and 1917. Grafter Mine shipped ore by the spur line from 1915 to 1917. Valerie was the last mine to ship ore over the spur line, from mid-1917 to mid-1918. The Copper King shipped out about the same tonnage as the Valerie although it was a higher grade. All of the Copper King's ore was shipped to the main WP&YR line by horse and wagon, or sleigh.
New technology and exploration techniques led to a second period of mining activity between 1967 and 1982. A haul road was constructed in 1970 to link the largest copper deposits and the ore was trucked to a railway loading facility on the Alaska Highway.
