Penn should not be in anybody's definition of the Region.
Depending who you ask, there's 2 definitions of the Region.
The first is the area known as the "Calumet Region". This is Hammond, East Chicago, Whiting, Gary, Munster, Highland, Griffith. You have to be an old school Region Rat to consider just this area the Region.
The "new school" definition of the Region includes pretty much all of Lake and Porter Counties. This would expand the "old school" definition to include Lake Central, Crown Point, Hanover Central, Lowell, Merrillville, Hobart, Lake Station (aka Snake Nation), Portage, Valparaiso, Chesterton, Wheeler.