Daily Alta California, Volume 1, Number 104, 30 April 1850
REPORT FROM THE SELECT COMMITTEE
On the Derivation and Definition
of the Names of the several Counties
of the State of California, &c.
Mariposa. — The name of this county signifies “butterfly.” In the month of June, 1807, in one of their yearly excursions to the valley of the rushes (valle de los tulares) with a view to hunt elks, a party of Californians pitched their tents on a stream at the foot of the Sierra Nevada, and whilst there, mryiads of butterflies, of the most gorgeous and variegated colors, clustered on the surrounding trees, attracted their attention, from which circumstance they gave the stream the appelation of Mariposa. Hence Mariposa river, from which the county (also heavily laden with the precious metal) derives its poetical name.