The geologic history of Yosemite began about 500 million years ago when the Sierra Nevada region lay beneath an ancient sea. Thick layers of sediment lay on the sea bed, which eventually was folded and twisted and thrust above sea level. Simultaneously molten rock welled up from deep within the earth and cooled slowly beneath the layers of sediment to form granite. Erosion gradually wore away almost all the overlying rock and exposed the granite. Even as uplifts continued to form the Sierra, water and glaciers went to work to carve the face of Yosemite. Weathering and erosion continue to shape it today. It has been said that Yosemite is the classic example of a glaciated valley. It is in fact a unique glaciated valley. If it were a classic example then most glacier carved valleys would have "Half Dome" and "El Capitan" type formations. In fact, most glaciated valleys do not have such structures. What sets Yosemite apart is the unique set of joint planes in its granite. These joints make the granite susceptible to erosion, producing steep walled canyons.
The first human residents of Yosemite were Native Americans. It is unknown how many bands visited or lived in the valley, but the last to call it home were the Ahwahnechee, under the leadership of Chief Teneiya. After several battles with Major Savage and the Mariposa battalion and a brief resettlement near Fresno, Teneiya and the Ahwahnechee returned and then fled the valley and took refuge with the Mono Indian tribe. In 1853 they again returned to Yosemite Valley. What happened next depends on what historical source is used. Some accounts state that his braves returned to the Mono Village and stole some horses. The Mono then pursued them and killed most of the tribe including Chief Teneiya. Other accounts say that some of the tribe were killed by whites in retaliation for killings the Ahwahnechee may or may not have committed. The rest of the tribe dispersed after Chief Teneiya's death in 1853. By any account, by 1854 the Indian chapter of Yosemite had ended.
The first accounts of the magnificence of Yosemite were not believed at first. It was James Hutchings who contributed the most to Yosemite's fame. He led the first tourist parties into the valley in 1855. He brought an artist, Thomas Ayers, to record their discoveries. He published a set of articles, including Ayers' paintings which were quickly spread by other newspapers. By 1860, many felt the commercial interests including the lumber industry, would ruin Yosemite. At the suggestion of the influential Reverend Thomas Starr King and later Frederick Law Olmsted, Senator John Conness introduced a Park bill in the senate. It passed both houses of congress and on June 30, 1864 it was signed into law by Abraham Lincoln. Unfortunately, this park only included the Yosemite Valley and the Mariposa Grove. It would not be until 1890 under the pressure brought to bear by John Muir that Yosemite National park would be created.