Yosemite National Park The State of California, however, retained control of Yosemite Valley and Mariposa Grove. Muir also helped persuade local officials to virtually eliminate grazing from the Yosemite high country. The newly created national park came under the jurisdiction of the United States Army's Troop I of the 4th Cavalry on May 19, 1891, which set up camp in Wawona with Captain Abram Epperson Wood as acting superintendent. By the late 1890s, sheep grazing was no longer a problem, and the Army made many other improvements. The cavalry could not intervene to ease the worsening condition of Yosemite Valley and Mariposa Grove.
Geology of the Yosemite area Geology of the Yosemite area The exposed geology of the Yosemite area includes primarily granitic rocks with some older metamorphic rock. The first rocks were laid down in Precambrian times, when the area around Yosemite National Park was on the edge of a very young North American continent. The sediment that formed the area first settled in the waters of a shallow sea, and compressive forces from a subduction zone in the mid-Paleozoic fused the seabed rocks and sediments, appending them to the continent. Heat generated from the subduction created island arcs of volcanoes that were also thrust into the