SHELTER-BELT DEMONSTRATIONS ON THE GREAT PLAINS. 3 
AREA COVERED BY SHELTER-BELT DEMONSTRATIONS. 
The area covered by this work comprises the western half of the 
States of North Dakota, South Dakota, and that part of Montana 
and Wyoming lying east of the Rocky Mountains. The region is 
roughly 500 miles square and contains a wide variation in topogra- 
phy, soil, and climate. The area is shown inclosed by a heavy line in 
Figure 1. 
Fig. 1. — Map of the northern Great Flains, showing within the heavy line the area to 
which the cooperative shelter-belt demonstrations are restricted. The glaciated sec- 
tion of the area is indicated by the crosshatched portion along its northern and eastern 
sides. 
TOPOGRAPHY.* 
GLACIATED SECTION. 
The glaciers at different times extended across the Missouri River 
for distances ranging from a few miles to 40 or 50 miles. This 
1 Descriptions of the surface features of this region are taken in part from the fol- 
lowing publications : 
Calhoun, Fred. H. H. The Montana lobe of the Keewatin ice sheet. U. S. Geol. Surv. 
Trof. Paper 50 (ser. B. Desc. Geol. 79), 
p., 30 fig., 7 pi. (partly col.), 1906. 
Lapham, Macy H., et al. Soil survey of western North Dakota. U. S. Dept. Agr., Bur. 
Soils, Field Operations — Advance Sheets, 1908, 80 p., 1 fig., 6 pi., 1 col. map, 1910. 
Leonard, Arthur Gray. The surface features of North Dakota and their origin. In 
Quart. .Tour., Univ. N. Dak., v. 9, no. 3, April, 1919. 
Wright, G. Frederick. The Ice Age in North America and Its Bearing upon the Antiq- 
uity of Man, xviii, 648 p., 148 fig., 1 pi., 3 maps. New York and London, 1891. 
