What can we learn about San Francisco, according to the passage?

From this lookout we enjoy one of the most spectacular views of San Francisco. As you can see, [17A] the city rests on a series of hills varying in altitude from sea level to nine hundred and thirty-eight feet.
    The first permanent settlement was made at this site in 1776 when a Spanish military post was established on the end of that peninsula. During the same year, some Franciscan fathers founded the mission San Francisco de Asis, and about halfway between the two, a station was established for travelers.
    For thirteen years, there were fewer than one hundred inhabitants. But in 1848, with the discovery of gold, the population grew to ten thousand. That same year, the name was changed to San Francisco.
    By 1862, telegraph communications linked San Francisco with eastern cities, and [19B] by 1869, the first transcontinental railroad connected the Pacific coast with the Atlantic seaboard. [18C] Today San Francisco has a population of almost three million. It is the financial center of the west, and serves as the terminus for trans-Pacific steamship lines and air traffic. The port of San Francisco handles between five and six million tons of cargo annually.
    And now, if you look out to your right, you should just be able to see the east section of the Golden Gate Bridge, which is more than one mile long. The bridge spans the harbor from San Francisco to Marin County and the Red Wood Highway. [20B]It was completed in 1937 at a cost of thirty-two million dollars and is still one of the largest suspension bridges in the world.