the central region of a country or continent; especially a region that is important to a country or to a culture
"The president's famous speech focused on the values and traditions deeply rooted in America's heartland."
The central part of a region defined by geographical or non-geographical criteria, such as support for a political party, faith or similar.
"The senator's speech focused entirely on the values and concerns of his state's conservative heartland before moving to the urban centers."