Q: Context: The fault was identified in 1895 by Professor Andrew Lawson of UC Berkeley, who discovered the northern zone. It is often described as having been named after San Andreas Lake, a small body of water that was formed in a valley between the two plates. However, according to some of his reports from 1895 and 1908, Lawson actually named it after the surrounding San Andreas Valley. Following the 1906 San Francisco earthquake, Lawson concluded that the fault extended all the way into southern California.

Question: how far south does the san andreas fault run? Let's give stream of consciousness first:
To answer the question, consider the following: Following the 1906 San Francisco earthquake, Lawson concluded that the fault extended all the way into southern California. Therefore, the final answer is all the way into southern California.