Minnesota Power is designing and building the 224-mile (360 km), 500-kV Great Northern Transmission Line through some of the most extensive peat bogs found in the U.S.’s lower 48 states. Traversing these long stretches of wet and soggy no-man’s land, Minnesota Power installed hundreds of foundations at the only time of year the ground is solid: in the wintertime. Besides battling the bogs, the utility had to contend with intense cold, deep snow and an extremely limited construction window. The Great Northern Transmission Line (GNTL) is set to connect Minnesota Power to Manitoba Hydro across the U.S.-Canadian border. The line will connect on the border near Roseau, Minnesota, U.S., to Minnesota Power’s new 500/230-kV Iron Range substation in Blackberry Township, near Grand Rapids, Minnesota. When finished in 2020, GNTL will deliver up to 883 MW of hydropower to northern Minnesota, enabling Minnesota Power to diversify its energy sources, meet increasing demand, and supplement system reliability. Following are images of the challenging construction process, which first appeared in the August 2019 issue of T&D World. For the entire article, see "Challenging Terrain for a Transmission Build."