The San Andreas Fault runs through the center of Tomales Bay, past Hog Island.

Sometime around 1885, the United States government sold Hog Island to one Christian Kuschert, a German immigrant.

The island appears on a 1916 map of the area produced by the United States Geological Survey.

The next year, the Gahagans became publishers of the Point Reyes Light, the regional weekly newspaper.

[3][4] The island is now uninhabited, but remains of a structure and a small pier show evidence of prior human habitation.