The Heartland of the [?] continent is shaped like a [?], with the [?] along the top. It is almost [?] to see what the original [?] of the land looked like, since on [?] there, the white man began to change it [?]. Turned into [?] or built over with busy cities, towns and industrial plants, very little [?] is left. The people in the [?] developed and cultivated it over the last two [?]. The settlers were [?] by others. The [?], for instance, has probably had more [?] on the landscape of the area than any other [?]. Beavers built [?] which stop erosion and make the land even more fertile. The Heartland, which was formed by an [?], is one of the most interesting parts of the [?]. Some evidence of the [?] is clearly visible in the form of low [?]. Side by side with these signs of an earlier age are the great cities and [?] farms of the people who chose the land and changed it.