Three natural physiographic divisions cross Washtenaw County from northwest to southeast. The northwestern part of the county is occupied by the rough interlobate moraine of loose-textured soil, the Interlobate Lake District; a broad Clay Morainic Belt occupies most of the central part of the county; and in the southeastern corner of the county is found a low Lake Plain, once the bed of glacial Lake Maumee.

The Interlobate Lake District has a conspicuous system of moraines, making up a most irregular land surface. Steep knolls 100 to 200 feet in height are closely associated with basins, which are often deep, and some of which are occupied by lakes. Small, undrained depressions occur everywhere, producing thousands of acres of swamp and marsh land.

The Clay Morainic Belt occupies the region from just below Portage Lake to Ypsilanti. It is composed of glacial till plains and clay moraines extending from northeast to southwest. This area includes the highest land in the county, one hill exceeding and several approaching 1100 feet in altitude. Most of the area is high and rolling.

The old beach, marking the limits of the Lake Plain District, runs northeast from Ypsilanti to the county line above Cherry Hill, and southwest through Stony Creek to a point on the county line about eight miles west of Milan.

The native upland forests of the Interlobate Moraine District were composed chiefly of red, yellow, and white oak, with some smooth-bark hickory and sugar maple and a few shag-bark hickories. Here were also large areas of creeping juniper and a few small patches of ground hemlock (yew). On the flood-plains of the rivers and lakes were quite extensive swampy forests of soft maple, black ash, and white elm. Swamp oak and whitewood grew commonly in the drier situations toward the edge of the swamp conditions. The red-bud and red cedar were characteristic of the river banks. White pine probably never grew in the county, although a few trees occur on the south bank of the Huron River near Hamburg, a few miles north of the county line.

Tamarack bogs, some of large size, are abundant in the Interlobate Moraine District and occur commonly also in the Clay Morainic District, but are practically wanting in the Lake Plain District.

The Clay Morainic District was originally dominated by forests of oak and hickory. Several kinds of oaks, white ash, and several species of hickories, with shag-bark most characteristic, were most abundant. Mixed with these were elm, beech, sugar maple, black walnut, and butternut. On the higher ground many stands of quaking aspen were found. The forest was quite dense and little underbrush normally occurred. Tamarack bogs were common, and a small stand of black spruce occurred at the edge of Independence Lake. There are few flood-plains along the Huron River in this district, but along the river's edge were a few cottonwoods and sycamores, and many willows, some of large size. On the steep bluffs along the river was often a heavy growth of red cedar; and some large areas of procumbent juniper occurred. In this district were several open, level, sandy plains covered with a scattered growth of white and bur oaks and an undergrowth of hazel brush. These were known to the pioneers as "oak openings" or "plains." Lodi Plains in Lodi Township, Bur Oak Plains in Manchester Township, Sharon Plains in Sharon Township, and Boyden's Plains in Webster Township were the largest of these natural openings in Washtenaw County.

On the low lands of the Lake Plain District great forests of black ash, elm, whitewood, soft maple, red-bud, swamp oak, and bur oak were found by the early settlers. Large sycamore trees were found along the river banks, these following the Huron River up a short distance beyond Ann Arbor and occurring all along the Raisin and Saline rivers. The paw paw and pin oak were found rarely in the southeastern part of the county. Along the small streams in this district were extensive marshes which were evidently old beaver meadows. About the edges of the marshes were fringes of tamaracks.

At the beginning of the nineteenth century Washtenaw County was an unbroken wilderness, and deer, wolves, bear, and other large and small fur-bearing animals were abundant. A few white trappers were in the region, and the Indians frequently passed through on the old Tecumseh Trail to Detroit, where they went to trade.

In 1809 three Frenchmen established a trading-post at Ypsilanti, where the Tecumseh Trail crossed the Huron River, and for several years they traded here with the Indians. In 1823 the first permanent settlement in the county was made by Benjamin Woodruff and two others at Woodruff's Grove, not far from the present site of Ypsilanti. A settlement was made at Ann Arbor in 1824, and many pioneers arrived in the county during the next few years.

With the coming of the settlers and the clearing of the forests the natural mammal habitats were greatly altered or destroyed. This, together with the hunting by the settlers, caused the gradual disappearance of the larger mammals, such as the cougar, bear, wolf, lynx, and deer. The clearings of the settlers created new habitats which were gradually occupied by species better adapted to civilization, such as the mole, woodchuck, ground squirrel, fox squirrel, and skunk, and also the house mouse and Norway rat, which were brought in unintentionally by the settlers.

For sixty-five years I have lived almost constantly in Washtenaw County and I have seen the latter part of the exploitation of the forests of the county and the extermination of most of the larger mammals. From my father, who settled in the county in 1836, and other old pioneers I have drawn extensively for information about the early mammals of the county. Much use has also been made of information contained in the Michigan Historical Collections. The specimens on which the records here are based are mostly preserved in the Museum of Zoology.

For considerable assistance in the preparation of the manuscript of this paper I am indebted to L. R. Dice, Curator of Mammals in the Museum of Zoology, University of Michigan.