MARIPOSA COUNTY COURTHOUSE (5088 bullion street) is California's oldest seat of justice still in use today west of the Rocky Mountains. The front half, the original building, completed in 1854, cost $9,200 to build.  The lumber was sash-sawed from near-by forests; framework fastened with mortised joints and wooden pegs. Finishing lumber was hand-planed and nailed with square-cut nails. A fire proof brick vault, to protect records, was added in 1861 and was later enlarged.  The English made clock with its 267 pound bell, in the cupola, was installed in 1866 and has been faithfully tolling each hour since.