Available at the Family History Library.
Also: This appears to be a reprint of an atlas originally published in 1876, available from Waynesburg University, both on the Web site for their media collection and in their library. See http://wcmedia.waynesburg.edu/index.php?cat=85
Bibliographical entry for the original:
J. A. Caldwell, Caldwell's Illustrated Combination Centennial Atlas of Greene Co. Pennsylvania: from actual surveys by & under the directions of Henry Gring, G. E. (J. A. Caldwell, Condit, Ohio, 1876).