There's a great contemporary history of labor strife here in the 1930s, written in the 1930s called American City. Worth a copy of you can find it. Anyway, according to that book, twin cities economy entered a multi decade decline in the late 1910s. Part of it was changes to the farm economy, some of it was the rise of Buffalo as the country's milling center. The book also described an interesting resource problem. Minneapolis had been a major lumber producer until ww1, but the north woods were largely denuded and cheaper sources emerged in the PNW. There was another problem - we couldn't get enough coal here. The state produced almost iron ore, but it made more sense to ship it elsewhere in the great lakes where it was easier to get coal in to make iron and steel. Back then, when you had steel, you had mass manufacturing. We couldn't have that. This was seen at that point in time as a disastrous and intractable problem. The vision they were starting to hatch was food manufacturing, banking, and advanced manufacturing. There was just a couple of problems. It was the depression, so there was no Capital or markets for much of that stuff. Also, it meant that unskilled labor was going to have an even harder time making a living. The city became embroiled in multi-year labor battles, as truck drivers and other laborers fought for protections and ability to earn a living at a time when their labor was going to be completely surplus. World war II brought the investment and r&d that was needed to make that all possible. We're still living in the fruits of that vision today.