'Hampden County, MA' definitions:

Hampden -- U.S. County in Massachusetts

From: Gazetteer 2000
Name :
Hampden -- U.S. County in Massachusetts
Population (2000) :
456228
Housing Units (2000) :
185876
Land area (2000) :
618.403870 sq. miles (1601.658602 sq. km)
Water area (2000) :
15.712396 sq. miles (40.694918 sq. km)
Total area (2000) :
634.116266 sq. miles (1642.353520 sq. km)
Located within :
Massachusetts (MA), FIPS 25
Location :
42.127560 N, 72.571312 W