What is "bull valley"

Population (2000): 726
Housing Units (2000): 281
Land area (2000): 5.609443 sq. miles (14.528390 sq. km)
Water area (2000): 0.000000 sq. miles (0.000000 sq. km)
Total area (2000): 5.609443 sq. miles (14.528390 sq. km)
FIPS code: 09531
Located within: Illinois (IL), FIPS 17
Location: 42.316132 N, 88.366815 W
ZIP Codes (1990):
Note: some ZIP codes may be omitted esp. for suburbs.
Headwords: