Semi-Centennial Geyser is located just north of Roaring Mountain in Yellowstone National Park in the U.S. state of Wyoming.

[2] Situated next to the Grand Loop Road, the geyser was first noticed when it had a few small eruptions in 1919.

By the afternoon on the same day reports stated that the ejected water was exceeding 300 feet (91 m) in height.

By the evening of the 14th, the geyser had scattered debris and rocks a distance of 450 ft (140 m) from the crater.

[3] As the geyser showed its biggest activity in 1922, the 50th anniversary of the establishment of Yellowstone National Park in 1872, it was accorded the name of Semi-Centennial.