Postcard of Liberty Cap photographed by Asahel Curtis, 1928. This 37 foot hot spring cone marks the northern portion of Mammoth Hot Springs. Liberty Cap was named in 1871 by the Hayden Survey party because of its marked resemblance to the peaked caps worn during the French Revolution. Its unusual formation was created by a hot spring whose plumbing remained open and in one location for a long time. Its internal pressure was sufficient to raise the water to a great height, allowing mineral deposits to build continuously for perhaps hundreds of years. Yellowstone National Park is a national park located primarily in the state of Wyoming, although it also extends into Montana and Idaho. It was established by the U.S. Congress and signed into law by President Ulysses S. Grant on March 1, 1872.