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In 1882, when Texas frontier judge Roy Bean began calling himself the "Law West of the Pecos," he was referring to the Pecos River, which flows from the mountains of New Mexico for almost 1,000 miles down through West Texas to the Rio Grande. The Pecos is an important source of water in the northern reaches of the Chihuahuan Desert—and that's how it attained its most unusual geographic distinction. Near Carlsbad, Mexico, locals brag, the Pecos becomes the world's only river that crosses itself.
• How can a river cross itself? In 1887, a group of settlers drew up plans for an irrigation canal on the Pecos, to irrigate crops in the semi-arid Pecos Valley. A series of hastily built dams and canals began to appear, and soon orchards and farms dotted the valley.
• The centerpiece of the project was a massive wooden flume. Supported by trestles, the 145-foot flume carried eight feet of water south through the main canal, crossing over a bend in the Pecos. Since water from the Pecos River was being carried across the Pecos River, Robert Ripley's Believe It or Not comic strip made the flume famous as the "World's Only River That Crosses Itself!"
• The flume carried 9,000 gallons of water a second, and its planners had lofty dreams of irrigating half a million acres. But the new canal proved no match for the region's flash floods. The flume was washed away and rebuilt in 1893, and within a decade the replacement was ready to collapse as well. With the help of the federal government, the wooden flume was replaced in 1903 with a majestic concrete version 47 feet high. At the time, the 497-foot structure was the largest concrete aqueduct in the world.
• Today, tourists still visit the Pecos River Flume, but it's seen better days: what was once one of the nation's premiere engineering feats is now a leaky, weed-choked overpass. But climb up the ruin and take a look: after heavy rain, water still flows through the channel above and along the rocks below. The Pecos River, over a century after Robert Ripley made it famous, is still crossing itself.
Explore the world's oddities every week with Ken Jennings, and check out his book Maphead for more geography trivia.