James died July 30, 1896 leaving two children, Edith L. and James Forest Lee. James left an estate of approximately $24,000. The Lee operations closed in the early twenties.
The Twin Mines were so named because there were two shafts, one on either side of the Milwaukee Railroad as it began to pass through the northern edge of Brazil. Both these shafts were 40 feet and led to long tunnels to the two mines proper, which were both located in the extreme southwest corner of Mystic. The two mines were sunk in 1893. Fred Baker was killed in the Lee Bros. Mine in 1907 when caught by a fall of coal. There was a waste dump on either side of the railroad tracks for some time. The dump on the south side of the tracks caused dirt to fall into Big Walnut Creek, causing it to flood. Richard Campbell owned some land on the south side of the creek so negotiated with the Lee brothers to desist dumping dirt there. At that time, they joined the two shafts together underground so no more waste was dumped in Big Walnut Creek. The two mines covered 87 acres by the time they were closed in 1919.