Originally Posted by RaY_Z
Actually, if I remember correctly, Lana mentioned in the reunion to Clark, that it was the first time he'd been back to Smallville since his mom past away.
In III Lana said that meaning Martha died sometime between the period after STM and before III. In IV Clark is selling the farm. She's still alive during the later parts of STM because Kent wanted part of his salary sent to his mother.