In general:
D1-AA top tier is located away from quality D1-A programs. i.e. North/South Dakota
D2 top tier is located away from quality D1-AA programs. i.e. Michigan
D3 top tier is located away from quality D2 programs. i.e. Ohio, Illinois
D3-wise
Mt. Union is pretty close to quality D2 programs in the PSAC West.
Saint John's (MN) dynasty was still surrounded by quality D2 programs both in state and the surrounding areas.
Wisconsin Whitewater is surrounded by a great D2 conference in the Great Lakes with Ferris/Saginaw/etc..
During the heyday of the PSAC, Washington and Jefferson as well as Lycoming were top 10 teams year in and year out. Susquehanna and Grove City are seeing a major resurgence in the heart of PSAC territory.
D2-wise
During West Chester, Bloomsburg, and Millersville's run in the 80's and 90's, they were all competing with Delaware and the rest of the Yankee and Atlantic 10 for athletes. In the west schools like IUP, Slippery Rock, etc were all competing with Youngstown State for athletes.
In the South, North Alabama was surrounded by quality D1AA schools in the 90's..
D1AA-wise
During Georgia Southern's run they obviously were surrounded by SEC and ACC schools as was App. State. When Marshall was 1AA they were competing with WVU, VA Tech, Kentucky, Tennessee in their backyard.
James Madison was in the heart of ACC/SEC country.