Montana ( Valley county) porcupine valley surveyed in 1909-1910 , Scale [1:62500] Scale [5:20] Contour Interval 20 Feet - Washinngton US Geological Survey 1918 - 1 Map Coloured 52 x 42 cm

Datum is mean sea level Approximate mean sea declination, 1916

Index Terms--Genre/Form:
Topographic Map

Dewey Class. No.: 912.786