Final answer:
The dense population center of San Francisco/San Jose can be attributed to the San Francisco Bay's sheltered harbor and strategic military location, coupled with historical events like the Gold Rush and World War II, as well as the development of a comprehensive public transportation system.
Step-by-step explanation:
The geographic feature that gave rise to the dense San Francisco/San Jose population center is the presence of the San Francisco Bay and its surrounding geographic attributes. The San Francisco Bay provided a sheltered harbor site, critical for trade and transportation, attracting immigrants and settlers during various historical periods. Additionally, the military strategic importance of this location, with El Presidio Real de San Francisco established for its defensibility, contributed to early settlement and growth.
Different periods of growth were marked by events such as the Gold Rush, where San Francisco rapidly evolved from a small town to a booming city, and World War II, which saw vast urbanization due to industrial expansion in the defense sector. The existence of a robust public transportation system, including an extensive rail network, further supported the urban growth and development of the Bay Area. These elements combined to create a hub of economic activity and cultural diversity that continues to draw people to this day.