Though iron has to be imported,--there being little mined in California,--the city does a thriving iron business. In the early days there was need of mining machinery in the West, and San Francisco at that time began manufacturing it. She also has one of the greatest shipbuilding plants in the United States. The famous battleship _Oregon_, the _Olympic_, the _Wisconsin_, the _Ohio_, and other ships of the United States Navy were built in San Francisco. [Illustration: THE CITY OF SAN FRANCISCO] In 1906 a severe earthquake shook San Francisco, wrecking many buildings. Fire broke out in twenty places, and as the earthquake had broken the city's water mains, the fire fighters had to pump salt water from the bay and use dynamite to stop the progress of the flames. During the three days of the fire, four square miles were laid in ruins. [Illustration: ON SAN FRANCISCO'S WATER FRONT] Because of occasional slight shocks in former years, the inhabitants had built their city of wood, thinking it safer than brick or stone. They had not thought of the greater danger of fire. This earthquake taught them a lesson. The few skyscrapers in the city had stood the shock remarkably well, and profiting by this experience thousands of modern structures--steel, brick, and reënforced concrete--were built to replace the old wooden buildings. A far more modern and beautiful city has arisen from the ashes of the ruins. [Illustration: CHINATOWN] The city occupies 46-1/2 square miles at the end of the southern peninsula which lies between San Francisco Bay and the Pacific Ocean. The site of the city is hilly, especially in the northern and western parts. Market Street, 120 feet wide and the chief business thoroughfare, extends southwest from the water front and divides the city into two parts. The southern district contains many manufacturing plants and the homes of the laboring people. The streets here are level. North of Market Street lie three high hills--Telegraph Hill, Nob Hill, and Russian Hill. In this half of the city are the finest residences, Nob Hill having been given its name in the early days when the mining millionaires built their homes upon it. [Illustration: THE UNION FERRY BUILDING] The main business section is in the northeastern part of the city, facing the harbor, and is on level ground. It contains hundreds of new office buildings, many of them from eight to twenty or more stories high. Fine modern hotels and beautiful banks add much to the beauty of this part of San Francisco. The most important public buildings are the United States mint and the post office, which escaped the flames in 1906, the customhouse, the Hall of Justice, the new Auditorium, and the city hall. These last two face the Civic Center, which is being created at a cost of nearly $17,000,000.