History of Mariposa, California
Taken from the California Gold Country. (Links Added)

The poetic name Mariposa, Spanish for “butterfly,” was first applied in this region by members of the Moraga Expedition, to a small stream at the foot of the Sierra Nevada mountains. The party had left the Mission San Juan Bautista on September 21 of 1806, on an expedition to locate suitable sites for a proposed string of inland missions to parallel those located along the coast. Led by Alferez Gabriel Moraga, they crossed the San Joaquin River on September 27 and during that afternoon encountered, “myriads of butterflies, of the most gorgeous and variegated colors, perched about on the surrounding trees.” Camping that evening on a slough not far from the main river, the chaplain and diarist of the expedition, a Franciscan priest named Father Pedro Munoz, made this entry for September 27, 1806: “This place is called the Mariposas because the great multitudes of these, especially at night and in the morning, could not be more troublesome, their eagerness to hide from the rays of the sun reaching such proportions that they pursued us everywhere, so much that one got into the ear of one of the Expedition Leaders, causing him great discomfort and not a little effort to extract it.”

Page 1