10 ILLINOIS BIOLOGICAL MONOGRAPHS [108 
PHYSICAL FEATURES OF THE BIG VERMILION BASIN 
The Big Vermilion River drains about 1,500 square miles in Champaign, 
Ford, and Vermilion counties in Illinois and a small portion of Warren and 
Fountain counties, Indiana. The North Fork also drains from a small 
territory in the southeastern part of Iroquois County, Illinois. The main 
stream, known as Middle Fork, rises in the southern part of Ford County 
near the town of Melvin, in the Bloomington morainic system, at a height 
of 800 feet above sea level. Its course is southeastward, between the hills 
of the moraine known as the Roberts and Melvin ridges, passing through 
the latter and uniting with a tributary known as the West Branch of the 
Middle Fork, which also rises at an elevation of 800 feet in the Roberts 
ridge. At Potomac, the stream turns southward, cuts through the outer 
ridge of the Bloomington moraine and crosses the plain of the Champlain 
till sheet, uniting with the Salt Fork about six miles west of Danville. 
The largest western tributary, known as the Salt Fork, rises in the till 
plain in the north-central part of Champaign County, near Thomasboro, 
at an elevation of about 740 feet above the sea. It drains the till plain 
lying between the Bloomington moraine on the north and the Champaign 
moraine on the south. It flows in a south and east direction for about 
55 miles! and unites with the Middle Fork as described above. A large 
tributary of Salt Fork, known as Spoon River? rises in the northeastern 
part of Champaign County, in two branches, not far from the outer ridge 
of the Bloomington moraine. Its general course is southward for a dis- 
tance of about ten miles, where it unites with the Salt Fork near St. Joseph. 
Another large tributary is known as the North Fork, which rises in the 
southeastern corner of Iroquois County in the inner ridge of the Blooming- 
ton moraine. It flows southward, cutting through the middle and outer 
ridges of the moraine, crosses a part of the Champaign till plain and unites 
with the Big Vermilion at Danville. This tributary has a length of about 
40 miles. From Danville the larger stream flows southeastward for about 
20 miles, crossing a part of Vermilion County, Indiana, and empties into 
the Wabash River 10 miles from the Illinois State line. 
The basin of the Big Vermilion River lies in or is surrounded by glacial 
moraines of the Early Wisconsin glaciation, the Bloomington moraine on 
1 Length of rivers designates total length including all meanders, 
2 Not to be confounded with Spoon River entering the Illinois River near Havana, Mason 
County. 
