The geysers and hot springs of Yellowstone National Park are a wonder of the natural world. They serve as vents for the geothermal energy below ground. And they are a delicate treasure that people have tried to ruin at every turn by throwing things into. This can alter the environment, sometimes permanently. And it started even before Yellowstone was a national park.
Yes, one of the most famous tales from that era is that an early expedition party used Old Faithful as a washing machine. According to an account shared by Frank D. Carpenter in his record of a trip to Yellowstone in 1877, The Wonders of Geyser Land, he and his traveling companions came upon Old Faithful and decided to experiment with “boiling” their clothes clean. The group put their soiled clothes in a pillowcase and threw it into the geyser’s cone. When it erupted, the clothes were sent flying over a hundred feet into the air. When they collected them, the churning, heated water had indeed cleaned them.
Emboldened by the results of their laundry experiment, they then clogged the geyser with “at least a thousand pounds of stones, trees, and stumps.” The geyser expelled all the rubbish and debris they’d choked the feature with, and they seemed pretty happy. As Carpenter says, “[Old Faithful] furnishes entertainment of unusual magnitude and duration.”
Even today, although it's illegal, people throw stuff into the geysers and springs. Sometimes specialists try to clean them out, but the process of doing so can cause damage to the delicate natural treasures. Read about the custom of throwing things into the geysers of Yellowstone at Atlas Obscura.