Primero was first and foremost a coal mine, and it provided work for the many people who lived in the town. Primero was one of the more productive mines that CF&I ran, producing over 8,000,000 tons of soft, bituminous coal over the course of its life. Bituminous coal has a high bitumen content and is used for making coke. Coke is a fuel used in the steel-making process, where raw coal is heated in a high-temperature oven without oxygen to remove impurities, allowing it to burn hotter. Bituminous coal, however, produces high amounts of gasses that without proper mine ventilation will cause explosions. Primero suffered two such explosions, one in 1907 and the other in 1910.
On top of the mining facilities, which included boiler houses, various shops, and the tipple, Primero had a lumber treating mill, a mule barn, and a feed barn.