Via The Writer’s Almanac:
It was on this day in 1875 that the largest recorded swarm of locusts in American history descended upon the Great Plains. It was a swarm about 1,800 miles long, 110 miles wide, from Canada down to Texas. North America was home to the most numerous species of locust on earth, the Rocky Mountain locust. At the height of their population, their total mass was equivalent to the 60 million bison that had inhabited the West. The Rocky Mountain locust is believed to have been the most common macroscopic creature of any kind ever to inhabit the planet.
Swarms would occur once every seven to twelve years, emerging from river valleys in the Rockies, sweeping east across the country. The size of the swarms tended to grow when there was less rain—and the West had been going through a drought since 1873. Farmers just east of the Rockies began to see a cloud approaching from the west. It was glinting around the edges where the locust wings caught the light of the sun.
People said the locusts descended like a driving snow in winter. They covered everything in their path. They sounded like thunder or a train and blanketed the ground, nearly a foot deep. Trees bent over with the weight of them. They ate nearly every living piece of vegetation in their path. They ate harnesses off horses and the bark of trees, curtains, clothing that was hung out on laundry lines. They chewed on the handles of farm tools and fence posts and railings. Some farmers tried to scare away the locusts by running into the swarm, and they had their clothes eaten right off their bodies.
Similar swarms occurred in the following years. The farmers became desperate. But by the mid 1880s, the rains had returned, and the swarms died down. Within a few decades, the Rocky Mountain locusts were believed to be extinct. The last two live specimens were collected in 1902, and they’re now stored at the Smithsonian.