xii Birds of Colorado 
PuysicaL FEATURES OF COLORADO. 
The State of Colorado lies near the centre of the United 
States, about two-thirds of the distance from the Atlantic 
to the Pacific coasts. It is quadrilateral in shape, measur- 
ing about 276 miles from north to south, and about 375 
from east to west. It has an area of about 103,900 
square miles. 
In general terms, the eastern third of the State consists 
of open, bare, dry plains, where the country is flat or 
rolling, and where there is hardly any timber except 
along the river bottoms. The elevation of these plains 
(the prairies) rises from about 3,500 feet at the Kansas 
border to 6,000 feet at the foothills of the Rocky 
Mountains. 
West of the 105th meridian, and rising with extra- 
ordinary abruptness from the plains to the east, the 
Rocky Mountains occupy roughly the middle third of 
the State. In a very general way the system forms 
two parallel ranges running north and south, joined by 
subsidiary east and west connections; between these 
are the great mountain parks, open wide valleys rather 
bare of trees, and situated at elevations of 7,000 to 
8,000 feet. 
The chief of these are North and South Parks, drained 
by the North and South Platte rivers, which meet out in 
the plains of Nebraska and join the Missouri near Omaha ; 
Middle Park, drained by the Grand River, the principal 
affluent of the Colorado River of the west, draining into 
the Gulf of California; and the San Luis Valley, draining 
into the Rio Grande on the south. 
The western third of the State consists, to a large 
extent, of a series of descending plateaus through which 
the rivers, all tributaries of the Colorado, have cut cafions 
