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. LIST OF SPECIES _Didelphis virginiana virginiana._ Virginia Opossum.--This species is rare in the county. One was taken by my father, Jessup S. Wood, in 1845, in Lodi Township. We have later records for Ann Arbor, Dexter, Manchester, Saline, and Scio Township. The last recorded specimen was taken by some boys in November, 1921, just south of the Oakland County line. February 5, 1912, a trapper took a specimen near Ann Arbor on a night when the temperature was about 10° F. below zero. _Scalopus aquaticus machrinus._ Prairie Mole.--The mole was rare or absent from the county when first settled, but it has gradually increased and has spread over most of the cultivated lands. It is most common in sandy or gravelly loams, and is absent from the hard clay soils. I remember the first appearance of the species on the old Wood homestead in Lodi Township about 1870. It soon became common. _Condylura cristata._ Star-nosed Mole.--Although not very rare in this county, it is seldom seen. We have records for Lodi Township, Ann Arbor, Webster Township, Ypsilanti, and Chelsea. It prefers low, marshy land near the water, and much of its food consists of aquatic insects, which it secures by swimming. It is not as well adapted for burrowing as the preceding species, so it lives in softer soil.