Mining happened in what is now the city of Houghton itself, where the Sheldon Columbian Mine operated near what is now called Tram St. There were several shafts and mining happened from about 1964-70. What follows was found in the mindat.org website:

“In June of 1864, the Sheldon Mining Co. and the Columbian Mining Co. merged, forming the Sheldon and Columbian Copper Co. At the time of the merger, the Columbian had two working shafts; the Sheldon five. After the merger, three of the shafts were closed and used for winzes to connect operating levels of the mine. The remaining four were named Stewert #1, Stebbins #2, Banker #3, and Bloodgood #4 (thought to be the mine captains at the time of merger). The mine worked the Isle Royale lode, which was known at the time to be rich in copper and silver. Operations continued until 1870 when erratic mineralization of the lode at depth forced the company to close. Since the opening of the Sheldon in 1853, 1,463,000 lbs. of copper were mined from this location. Copper crystals, silver, datolite, and chalcocite can be found here.”

At this site remnants of the mine dump can be seen, but a house is now built right on top of the mine dump!  The former shaft locations are uncertain.  Many places in Houghton, especially along the same horizons, could be subject to unstable ground. A former mine was found when excavation for the present mineral museum was made and the former Houghton Transfer station just uphill from this site had to be moved after its construction because its walls were cracking.