From the Guidebook:
This is the site of the ferry
crossing established in 1860 by Thomas H. Parrott that
connected the mining towns of Tuttletown and Vallecito.
The ferry was in operation until 1903, when the first
bridge was built. The ferryboat, of flatbottom wooden
construction, was propelled on heavy cables anchored in
a large boulder. Still visible (1949) at low water on
the Calaveras side of the river is the sandbag dam built
to form a small lake that stored enough water to float
the ferries in dry periods.