 Military expeditions during the Mexican Era history of California passed through the Merced River region in the early 19th century . The California Gold Rush brought many people into California and some settled leading to the establishment of a railroad along the river , bringing minerals and lumber to towns that had been established on the lower Merced , and later provided tourism to the now @-@ national park area . Conflicts between whites and indigenous peoples prompted wars , resulting in the expulsion of the Ahwahnechee from Yosemite Valley . In the 20th century , the river saw further development that would change its state forever . 
