Albert Barnes Commentary 1 Kings 12:25

"Then Jeroboam built Shechem in the hill-country of Ephraim, and dwelt therein; and he went out from thence, and built Penuel." — 1 Kings 12:25 (ASV)

Built Shechem - This means he “enlarged and fortified” it . Jeroboam’s first intention seems to have been to make Shechem his capital, and therefore he immediately began its fortification. He also appears to have fortified Penuel to better secure his possessions east of the Jordan River (as noted in the marginal reference).