Amur Maple - Acer ginnala and Siberian elm - Ulmus pumila, both are classed as invasive species in most, if not all of the USA & Canada. The best thing to do is find them in the landscape, and collect them. Thus removing them from the ecosystem, and you don't have to fell guilty if you kill them. Acer ginnala (amur maple) is not the worst of invasives, some nurseries may still sell them. They have a nice autumn color, the most often cultivated form has red & yellow autumn color, the less domesticated forms have a nice clear yellow.
Amur maple tends to be pretty angular in its branch pattern, it doesn't make smooth arching curves, unless you put a lot of effort into creating smooth curves. Best to design to use the angular features of Amur maple. Amur tend to have short, then long internodes, the internode length can be irregular, another feature to be aware of, but easy enough to work around.
In zone 5, and even zone 4b, Amur is hardy enough to simply just set the pot on the ground, with no other added protection and it will pull through the winter without loosing a twig. Incredibly winter hardy. If you are in zone 4a or 3b you would need to perhaps shelter it from dry winter wind, and winter sun, but otherwise they are very hardy. Similar hardiness applies for Siberian elm.
Siberian elm is an excellent elm for bonsai - with one caveat. You MUST keep them in full sun, sunrise to sunset full sun. If they are partially shaded, they have the bad habit of dropping branches on the shady side of the tree. Leaves are naturally small, and reduce nicely as bonsai. Wonderful rough bark. Really a great elm for bonsai.
American elm, Ulmus americana, and rock elm, Ulmus thomasii are both native to Minnesota, are very hardy and make good bonsai. Both are more shade tolerant than Siberian elm. In cultivation, they will be small enough so that beetle that spreads the ''Dutch Elm Disease" will not find them. In a container, or bonsai pot, it is possible to treat and clear up Dutch elm disease. They can be used in the same way Chinese elms are used, but significantly more winter hardy. Autumn colors tend to be just a clear yellow.
Carpinus caroliniana - American hornbeam - is a native to Minnesota, it is somewhat like a beach in appearance, but much easier to grow, needs a certain amount of shade, not good for all day full sun. Lovely autumn colors with oranges predominating.
American larch, Larix laricina, and European larch, Larix decidua, are both good for Minnesota. The Japanese larch may be at its cold tolerance limit in Minnesota. Great for bonsai.
Spruce - there are a number of good spruces that make excellent bonsai, the native Picea glauca - white spruce, and the near native Black Hills spruce - Picea glauca densata, are great candidates for winter hardy Minnesota bonsai. The dwarf Alberta Spruce is a mutant variation of Picea glauca, and is just okay for bonsai - it has some quirks that one needs to learn how to handle, go for the wild type, or reforestation type of white spruce that is just labeled Picea glauca, and you will have a better bonsai with less effort.
Black spruce - if you can collect naturally stunted ones from the cranberry bogs and norther muskeg. these are fantastic for bonsai. They prefer an acidic soil and definitely need a cold winter to thrive.
American White Cedar - Thuja occidentalis - is fantastic as bonsai. Not really a beginner tree, but may as well start learning now. Super winter hardy, and very similar to a Hinoki. Native throughout all of Minnesota. Also known as Arborvitae. Nursery material is okay, but will lack character, collecting old stunted specimens that have been repeatedly chewed by deer will give you a tree with amazing character.
Hope these give you some ideas.
Scotts pine from the nurseries make good bonsai too.