Answer:

heartland

AnswerCrossword Clue
HEARTLANDCalifornia's Central Valley, e.g.
HEARTLANDMiddle America
HEARTLANDRegion symbolizing traditional values
HEARTLAND"Amber waves of grain" area
HEARTLANDVital region for a worm?
HEARTLANDMidwest and Plains states, e.g.
HEARTLANDMiddle of the country
HEARTLANDCountry's core