This large rattlesnake can be found in the cape region of lower Baja California and some surrounding islands. It can grow to nearly 4 ft long! It occurs in habitat including heavy brush and rocks. The San Lucan diamond rattlesnake is primarily nocturnal.

It is hypothesized this subspecies diverged from C. ruber ruber due to a large divide of unsuitable habitat sometime during the Pleistocene. In the present day, both subspecies have extended their range and now overlap in the area around Loreto.

This subspecies shows a slight tendency for rattle loss with less than half of individuals retaining a rattle after a shed! San Lucan Island rattlesnakes feature a blunted proximal (base) rattle segment which has less distinct lobes and grooves, thus increasing the chances of the new rattle segment failing to remain in place.