The One Minute Geographer: The Great Plains - The 100-Degree West Longitude Line

Jim Fonseca
2 min readOct 12, 2021
The 100th meridian in yellow; rainfall — red; elevation — blue; and grasslands — green. Base map from; lines drawn by the author.

The 100-degree west longitude line, the 100th Meridian (yellow on the map), is a fascinating line because it happens to closely coincide with other important geographical features of the United States.

Those other features include the 20-inch rainfall line (red), the line very roughly marking 2,000 feet of elevation (blue), and the midline marking about the center of where mixed-grass prairies were the original natural vegetation (green).

These geographic features very much influenced historical settlement of the Great Plains where these lines lie. And they continue to reflect important aspects of the climate which influences the types of crops that can be grown in these mostly agricultural areas.

We’ll be looking at each of these aspects reflected by these lines on the Great Plains, so follow me on medium for further posts. Here’s the next post in this Great Plains/Magical Meridian series

I’m a retired geography professor. Follow me on for more posts on The One Minute Geographer. You can get an email when I publish by clicking this link (6 or so posts each month):

Jim Fonseca

Geography professor (retired) writes The One Minute Geographer featuring This Fragile Earth. Top writer in Transportation and, in past months, Travel.