Cal. Gov. Code § 23122
The boundaries of Mariposa County are as follows:
Beginning on the boundary line of Madera County, where the Stockton road to Millerton crosses the Chowchilla Creek, known as Newton's crossing; thence north, 46 degrees E., to the southwest corner of Sec. 11, and the northwest corner of Sec. 14, in T. 6 S., R. 20 E., M. D. B. & M.; thence east to the northwest corner of Sec. 14, in T. 6 S., R. 21 E.; thence north to the northwest corner of Sec. 35, T. 5 S., R. 21 E.; thence east to the southwest corner of Sec. 30, in T. 5 S., R. 22 E.; thence north to the southwest corner of the Mariposa Big Tree Grant; thence east, along the line of said grant to the southeast corner of said grant; thence north, along line of said grant to the northeast corner of the same; thence north to the original boundary line between Mariposa and Fresno; thence northeasterly along said line to the boundary line of Tuolumne; thence westerly, by the southerly boundary of Tuolumne, to the southwest corner thereof, being the common corner of Stanislaus, Merced, Tuolumne, and Mariposa; thence southeasterly, on the eastern line of Merced, to the place of beginning.
Ca. Gov. Code § 23122