'Hill country' in the Bible

Abijah stood up on Mount Zemaraim, which is in the hill country of Ephraim, and said, "Hear me, Jeroboam and all Israel:

When Asa heard these words, and the prophecy of Oded the prophet, he took courage, and put away the abominations out of all the land of Judah and Benjamin, and out of the cities which he had taken from the hill country of Ephraim; and he renewed the altar of Yahweh, that was before the porch of Yahweh.

Jehoshaphat lived at Jerusalem: and he went out again among the people from Beersheba to the hill country of Ephraim, and brought them back to Yahweh, the God of their fathers.

Moreover he built cities in the hill country of Judah, and in the forests he built castles and towers.