Crossing the 100th Meridian

A re-peat, due to editing and Day Job.

The 100th Meridian is one of those things that is really, really important as a symbol and shorthand, and makes no sense to people from most of the rest of the world. It’s not officially designated like the 0 degree line in Greenwich, England is, it is not a date line like the 180th meridian is. If you cross it on I-40 in Oklahoma City, OK, for example, you will have seen a historical marker for the Chisum Trail, and will soon see a second marker (two main branches), but aside from Meridian Street, nothing. I don’t think I-20, I-70, I-80 or I-90 have anything on that invisible line. But it is important for hydrologists, botanists, and other students of the American West. So what is the big deal, other than an invisible line on a paper map that happens to be a round number?

The 100th meridian happens to be where the rainfall in North America drops to less than 20 inches per year, on average. This is the region where irrigation becomes necessary, where short grasses replace tall and mid-grasses, where ranching and sheep-herding are better long-term land uses than are many forms of crop raising. It is where the trees fade away, or did before Anglos and Hispanos insisted on planting them and suppressing fires. While Eurasia is divided by horizontal climate bands, North America is chopped up vertically.

Dry and/or lumpy – must be the American West.

In the days before more than buffalo, wolves, and Indians roamed the landscape, the 100th Meridian was where the steppe blended into the mid-grass prairies, and then the tall-grass. As wet and dry periods came and went with climatic fluctuations, the grass-line swept back and forth, east and west, and buffalo and people followed it. There were periods when the 20 inch line shifted to the Mississippi River valley, and periods when it marched west almost to the Rocky Mountains.

Today, the twenty-inch-line separates corn (maize) from wheat, especially winter wheat. To the east, irrigation is usually because of sandy soil and is not a requirement most years. To the west, irrigation is a fact of life, and a year without needing to run the pumps is seen as a gift from a benevolent deity, and considered quite notable. Grasses are shorter, and ranching makes far more sense as a land use than does farming or raising water-intensive livestock such as swine. To the west of the meridian, prior-appropriation doctrines determine who gets how much water from what source. East of the line, riparian rights dominate, with a few exceptions (although that may be changing as urban usage outstrips streamflow). Almost no one in Ohio, for example, worries about how much water his upstream or downstream neighbor is taking out of the river to water his crops. They are often far more concerned about how high the river is getting and will it flood the lower fields.

As a result, the 100th meridian is a convenient short hand for the American West and the mindsets and legal atmosphere of the region. It is pure coincidence that the meridian and the twenty-inch isoheyt happen to coincide most years. That coincidence, however, makes for useful definitions and quick border sketching. “Crossing the 100th Meridian” and “Crossing the Next Meridian” have both been used as book titles, both regarding the laws and land use philosophies of the American West, with all the variations and regional quirks that entails. There’s often a sense that people from east of the line don’t quite understand the problems and challenges of life to the west of the line. Or, conversely, that because the people at 101 degrees and beyond are too closely involved with local things to really appreciate the larger national and international picture, and so “outsiders” are badly needed to mediate and provide (or at least strongly suggest) solutions that include all parties, including the wildlife and landscape.*

You can’t see the 100th Meridian. There’s no highway that follows it, no state-designated scenic route, no national trail of the 100th Meridian, no sign saying “The West Begins Here.” The sky has already begun to grow larger, trees fewer, and towns more scattered. Those of us who live in the great central grasslands of North American know the line, we often cross it many times in our lives, and some of us feel more comfortable west of the divide. It is much a mental as a geographic stripe.

*In-stream rights is a legal concept arguing that fish, beaver, and other things have as much right to water from the river as do humans, if not more so, and their rights must be considered when water is appropriated and divided up among users.

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