Ulmus pumila makes decent bonsai - if you can give it full sun, dawn to dusk full sun. Will drop branches on the shady side of the tree.
Ulmus americana, and Ulmus rubra - make decent bonsai, leaves reduce well with branch ramification. Does not drop branches as easily as U. pumila.
Ulmus thomasii is native to Minnesota - it is the cold tolerant version of the Cedar elm, sometimes called Rock elm. This is worth seeking out for bonsai.