Knoxville was a mining town of about 300 people (50 houses) in it's heyday. The few mines in the area were all mining quicksilver (mercury). The town was predominantly Irish young men who sacrificed their health for the high pay.
The mines have all been abandoned and in some cases buried/remediated. By the mid 1980's all houses/buildings had been leveled and only a few stone walls remain to mark the town.
A more complete history of the town can be found at http://nrs.ucdavis.edu/mcl/natural/land/history.html