The eruption came without warning, and Yellowstone spokesperson Dan Hottle said the park estimates it reached between 200 and 300 feet high before steaming for around 24 hours.
Steamboat's eruptions are often impressive, but they're also unpredictable, with months or even decades between them. The geyser was dormant from 1911 to 1961, and later, it erupted 29 times in a single year.
The geyser's eruptions can reach up to 400 feet in the air and last between 3 and 40 minutes, and steam can spill out for up to 48 hours afterward.
It took park rangers two hours to arrive at Steamboat, one of Yellowstone's 300 geysers -- more than half the world's total. Rangers use electronic heat sensors on each one to notify them of an eruption, and in this case, park visitors called them as well.
Luckily, 30 to 40 visitors were on hand to witness the eruption, and quickly captured the event on their smartphones. Now, fans are energized to visit Yellowstone's geysers.
"For us, it's exciting. Every time you're down there, you wonder if that'll be the time that it erupts," Hottle said.