This paper uses mine-level data to study labour productivity in Ontario’s gold mining industry from 1920 to 1970. The ounces of gold produced by a mine worker are nearly identical in 1920 and 1970. Thus, the industry appears to experience no productivity gains over this period. In fact, labour productivity in the intervening years was nearly 30% lower than these values, raising concerns about the ability of the industry to re-main profitable given a fixed price for gold. Using a unique mine-level data-set for over 75 different mines comprising nearly 90% of the industry in Ontario, we perform a firm-level analysis of productivity. This analysis allows us to determine whether workers are in fact becoming less efficient over time, or whether other factors, such as entry and exit into the industry, declining quality of ore bodies, or changes in capital stock, are the primary drivers of this stagnation. We are also able to determine the impact that events such as a sudden 70% rise in the price of gold in 1934, the Second World War, and the subsidization of the industry in the late 1940s had on productivity.