Keystone Lodge No. 161, F. & A. M. was instituted in Copperopolis on Dec. 19, 1862, at the height of the copper mining boom. In 1881 it moved to Milton, the terminal of the Stockton & Copperopolis Railroad, which never reached its intended goal because of the collapse of copper mining. The hall is dedicated to those who sought to perpetuate the moral teachings of Freemasonry, and gratitude is expressed for their efforts.