Understanding Principal Meridians

I took a slight detour on Monday while traveling from Vincennes, Indiana to O'Fallon, Illinois, to see the the basepoint location of the 3rd principal meridian -- just south of Centralia.

America's principal meridians helped shape the nation's land pattern, while simplifying land title and transfers. I spoke with John Shankland, who has developed the principal meridian project web site, before departing on my trip. John is an enthusiast about geography and history, and will quickly fill you in on principal meridians, including the 3rd.  (about a 7 minute audio clip).

• to listen to the conversation [press blue arrow to play; click link to download]
• access this conversation on our podcast page

A map of America's principal meridians and their base lines (from the Bureau of Land Management). The 3rd principal meridian defined land within the section of Illinois shown in lavender.