The curved part of a stream or river is called a bend. The Rio Grande, marking the border between Texas and Mexico and deﬁning the 118 miles of the southern border of Big Bend National Park, abruptly changes its southeasterly ﬂow to the northeast and forms the amazing “big bend.” “Big,” of course. It’s Texas. Not just canyon rivers but alluvial rivers such as the Mississippi also have bends. A river moving through a 180-degree turn creates a horseshoe bend. Vicksburg, Mississippi, site of a famous Civil War battle, was once located on such a bend. And the Colorado River forms a horseshoe bend as it makes a wide sweep around an enormous sandstone escarpment in the stark canyonlands near Lake Powell, south of Page, Arizona. In My First Summer in the Sierra, John Muir wrote of attempting to force sheep across a stream: “They were driven into a horseshoe bend and fairly crowded off the bank. They seemed willing to suffer death rather than risk getting wet.” A clever use of a horseshoe bend.