The Great Northern was one of the first railroads in the United States to order Mountain locomotives. The manufacturer Lima saw these as Mikados, which had a two-axle forward bogie for better running characteristics in passenger service. The Great Northern wanted to use the P-1 to eliminate the need for helpers on passenger trains in Montana and the Cascades.

They had a conical boiler with a Belpaire firebox. The first ten P-1s were coal-fired and the last five were oil-fired. The diameter of the drivers was only 62 inches or 1,575 mm, which was an advantage on the steep lines. The speed of passenger trains was now 20 mph (32 km/h) on the 1.8 percent in Montana and 15 mph (24 km/h) on the 2.2 percent in the Cascades, both without helpers.

When these locomotives were no longer sufficient to meet the increased requirements, in 1928 all P-1s were rebuilt into 2-10-2 freight locomotives and designated class Q-2. The drivers and the cylinder diameter were each increased by one inch. The boiler only remained the same on the outside and had many changes on the inside, as well as a higher pressure. They were all coal-fired, but nine were converted to oil in the 1940s. Their decommissioning began in the 1950s and was completed in April 1958.