What is a Mima mound?

Dude.. some people need to stop copying their info from websites. Mima Mounds are named for the prarie in WESTERN Washington state, not SW Washington. Sure similar mounds may be found all over the world, but they are know by other names by their local villagers. Who knows why they were formed, but it is a good way to keep the greeners busy. These mounds probably originally covered most of the praries of the world, but the thousands of years of grazing, leveling, and harvesting the fields have flattened them.